Since all the functions in here are addition and subtraction, you can remove the parentheses and just combine like terms.
[tex](7x-6y)+(3x+3y-3) \\ 7x-6y+3x+3y-3 \\ 7x+3x+3y-6y-3 \\ (7x+3x)+(3y-6y)-3 \\ 10x+(-3y)-3 \\ 10x-3y-3[/tex]
The answer is 10x-3y-3.
Hope this helps!