I am not sure how to do this, but i have an example problem.
Hello, Joanna ---
I don't see an example problem, but will try to make one up.
Suppose you want to combine like terms of the following string:
(2x + 3) + (x -3y +7) - (2x + 4y - 6)
First, remove the parentheses by distributing the + and - signs across the second and third terms:
2x + 3 + x -3y +7 -2x -4y + 6
Now bring the x-terms together, then the y-terms and then the number terms:
2x + x - 2x - 3y - 4y + 3 + 7 + 6
Add all of the x-terms, the y-terms and the numbers:
x - 7y + 16
This would be your final answer.
These problems can be much more complicated, but this is the general idea.