How do I define my variables
So I try to define my variables like yearborn and currentyear and the call them later when I subtract the two but it will not call them
Your input is in the form of a string. In order for your equations to work, you need to convert your input from a string to an integer:
This will only work if your variables can be converted to integers. If the input was "three" for example, then it would fail when trying to convert to an integer.