Nead help with my calculator program- getting syntax error

[FantasyCookie17]

 
s=0
a=float(input("Enter number."))
b=input("Enter +, -, x, *, / or :.")
if b=="-":
    s=a-c
    c=float(input("Enter number")
if b=="+": 
    c=float(input("Enter number")
    s=a+c
if b=="x" or "*":
    c=float(input("Enter number")
    s=a*c
if b=="/" or ":":
    c=float(input("Enter number")
    s=a/c
print(s)
while True:
          b=input("Enter =, +, -, x, *, / or :.")
          if b=="+":
              c=float(input("Enter number")
              s=s+c
          if b=="-":
              c=float(input("Enter number")
              s=s-c
          if b=="x" or "*":
              c=float(input("Enter number")
              s=s*c
          if b=="/" or ":":
              c=float(input("Enter number")
              s=s/c
          if b=="=":
              print(s)
              quit()
          print(s)

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@buran The script won‘t start, it just says ‚„Syntax error“ at the „:“ after the first „+“. I also got syntax errors on the first „s“ if I used the „def“ thing for the second part of the script and then put it in the line under what is currently line 30 and so on. I used this script both in Python 3.6 (MacOS) and 3.7 (LinuxMint), and in both I got the same error. Maybe someone of you could find the problem by trying out this script themselves.