Question 1048515

{{{(7a^2-3b^2+10)-(-2a^2+b^2-12)}}}

recall the rules: 
When parentheses are preceded by a plus sign + simply remove them.  Nothing changes.
When parentheses are preceded by a minus sign - change the sign of every term within the parentheses.

so, you get

{{{7a^2-3b^2+10+2a^2-b^2+12}}}

{{{7a^2+2a^2-3b^2-b^2+12+10}}}

{{{9a^2-4b^2+22}}}