I wrote this simple code and tried to execute in Windows 10 CMD ... and it gets the error message :
TypeError: Can only concatenate str (not \"int\") to str
Convert age to int to do your maths:
finalAge = int(age) + factor
And as a bonus you could use the .format() option:
print("In {0} years you will be {1} years old, {2}!".format(factor, finalAge, userName))