To write a subtraction problem as an addition problem, just switch the numbers a little. For example:
11 - 5 = ?
Just write it like this:
5 + ? = 11
These two problems will get the same answer. Watch:
11 - 5 = 6
5 + 6 = 11
Both of these work because all three numbers ( two main ones and the answer) Can be switched around in different orders depending on the operation.
Hope this helps, WyattMarine501