Question 9006
Ok, first you are going to combine like terms, therefore adding 3a + 2a. You'll get 5a, right? Of course. 


Now your expression looks like this: {{{5a-(4a+7)}}}


Alright, you gotta get rid of that pesky little minus sign, so distribute it throughout the parenthesis. 


{{{5a+4a-7}}}


Combine like terms again.


{{{9a-7}}}


And there's your answer.