What have I done wrong?

[Gandalf]

So I am new to learning Phyton and I don't know what I did wrong here, I would appreciate it if you could help me and also if you could simplify your explanation a bit.

This is the code:

birthyear = input(' in what year were you born? ')
age = 2019 - int(birthyear)
print(' you are ' + age + ' years old. ')

And this is the error I get:

Error:
Traceback (most recent call last):
  File "C:/Users/alicf/PycharmProjects/NOOB/yildan yas hesabi/erdo.py", line 3, in <module>
    print(' you are ' + age + ' years old. ')
TypeError: can only concatenate str (not "int") to str