Question 75407
(5b-7ab+8a)-(5ab-4a)
Just drop the first set of parentheses
5b-7ab+8a
To "drop" the second set of parentheses, the - in front of it is like multiplying all terms inside the parentheses by -1,which changes all of the signs
-5ab+4a
Now combine everyone back into one expression
5b-7ab+8a-5ab+4a
Now combine like terms
5b-12ab+12a
Usually terms are put in alphabetical order,so rearrange that way
12a-12ab+5b