Creating a variable that displays time

[tannishpage]

Ok first of all restructure your code. How? Well you have functions inside a function, which is not a good idea because a function is meant for one process. So my suggestion is to make the code like this

from random import randint
def main():
    #Calls on the menu display (display_intro, and display_menu)
    dis_intro()
    dis_menu()

#Defines what the title will look like. Prints all visuals. (When called)
def dis_intro():
    title = "**A Simple, 10 question Maths Quiz**"
    author = "_____________ By Elijah ____________"
    print("*" * len(title))
    print(title)
    print("*" * len(title))
    print(author)
    
#Defines the user options. Prints all visuals. (When called)
def dis_menu():
    title = "**A Simple, 10 question Maths Quiz**"
    men_list = ["1. Addition", "2. Subtraction", "3. Multiplication", "4. Division", "5. Random 1-10"]
    
#Loops for the length of the list
    for i in range(0, len(men_list)):
        print(men_list[i]) #Prints
            
    print("-" * len(title))
        
    #Assigns a piece of either positive or critical feedback to a list, with a number to call apon.
    p_feedback = ["Correct, great job!", "Amazing, keep it up!", "Perfect!", "Good job!", "Keep it up!"]
    c_feedback = ["Wrong, nice try...", "Nearly...", "Not quite...", "Try again!", "Don't give up!"]
    
    #Asks what operation the user wants to use.
    choose = int(input("Enter your choice: "))
    print("")
    if choose == 1:
        addition()
      
    #Runs code for addition questions.
    def addition():
            print("Great, addition!")
            import time
            question = int(0) #Sets the question number to 0.
            score = int(0) #Sets the player score to 0.
            min_num = input("What will the minimum number be? ") #Asks for minimum number, and assigns it to a variable.
            max_num = input("What will the maximum number be? ") #Asks for the maximum number, and assigns it to a variable.
             
            #loops until the player has answered 10 questions.
            while question != int(10):
                num_1 = randint(int(min_num), int(max_num)) #Imports a random interger between the player specified range, and assigns it to a variable to use for the question generation.
                num_2 = randint(int(min_num), int(max_num)) #Imports a random interger between the player specified range, and assigns it to a variable to use for the question generation.
                answer = num_1 + num_2 #Sets a question to ask the player.
                guess = input("Answer: " + str(num_1) + " + " + str(num_2) + " = ") #Displays the generated question to the player, and allows an input.
             
                #Determines if the answer the players inputed answer matches the computer generated answer.
                if int(answer) == int(guess):
                    rand_f = randint(0, 4) #Generates a random interger to use to call up a peice of feedback from the list.
                    print(p_feedback[rand_f]) #Uses the randomly generated Interger to print the feedback from the list.
                    question = question + 1 #Adds one to the question number.
                    score = score + 1 #Adds on to the score of the player.
                    print("You are on question: " + str(question) + "/10") #Prints question number.
                 
                #Determines it the player answer is not equal to the computer generated answer.
                else:
                    rand_f = randint(0, 4) #Generates a random interger to use to call up a peice of feedback from the list.
                    print(c_feedback[rand_f]) #Uses the randomly generated Interger to print the feedback from the list.
                    question = question + 1 #Adds one to the question number.
                     
                #Determines if the player has answered 10 questions yet.
                if question == int(10):
                    print("")
                    print("Well done, you completed the quiz!") #Affirms player.
                    time.sleep(1)
                    print("You got " + str(score) + "/10 corect!") #Prints score.
                    print("")
                    time.sleep(1)
                     
                    #Defines what the title for playing agian will look like.
                    title_2 = "**Do you want to play again?**" #Defines the title.
                    print("*" * len(title_2)) #Prints * the length of the title.
                    print(title_2) #Prints the title.
                    print("*" * len(title_2)) #Prints * the length of the title.
                     
                    #Defines what the menu for playing again looks like.
                    title_2 = "**Do you want to play again?**" #Defines the title.
                    men_list_2 = ["1. Play again", "2. Exit"] #Defines the options the user has.
                     
                    #Loops for the length of the list.
                    for i in range(0, len(men_list_2)):
                        print(men_list_2[i]) #Prints.
         
                    print("-" * len(title_2)) #Prints _ the length of the title.
                    print("")
                     
                    choose_2 = int(input("What is your choice? ")) #Asks for player input.
                     
                    #Defines what will happen if the player chooses option 1.
                    if choose_2 == 1:
                        import time
                        print("")
                        print("Restarting Game")
                        print("Redirecting to menu.")
                        time.sleep(1)
                        print("...")
                        print("Loading Code.")
                        time.sleep(1)
                        print("...")
                        print("Reseting Variables.")
                        time.sleep(1)
                        print("...")
                        print("Wasting some time.")
                        time.sleep(1)
                        print("...")
                        print("Running Functions.")
                        time.sleep(2)
                        print("...")
                        print("")
                        time.sleep(1)
                        dis_menu() #Starts the menu again. #THIS HAS BEEN CHANGED
                         
                    #Defines what will happen if the player chooses option 2.
                    if choose_2 == 2:
                        print("")
                        print("Ok!")
                        print("Thanks for playing!")
                        print("")
                        print("Please come back soon!")
 
    #Calls on the code for each operation, depending on user input.
main()

Now for calculating the amount of time taken

from datetime import datetime
start = datetime.now()

#The addition quiz loop

end = datetime.now()

time_taken = (end-start).total_seconds()

that will give you the time taken for that function. you can put that when you start the function or when you start the loop.

Just saying, your structure is very illegibal. I would recommend you restructure the whole thing. Ask me for assistance if you need it. :)