It is adding 1+2 as 12 !!! Whereas substraction is perfect..

Question

https://code.sololearn.com/WBZJ6VJGd5u0/?ref=app

Answer 1

You should add parseInt function to make them numbers first.
See the code :-
https://code.sololearn.com/Wl4Wghz5Cv9e/#js

Answer 2

try: alert(Number(x)+Number(y));

- It is treating user input as a string.

Answer 3

It is just because the parameters are string. For the + operation the program will join x and y. But the - operator doesn't exist for string, so the program will convert x and y to integers.