Question 75407:  (5b-7ab+8a)-(5ab-4a) 
 Answer by cathieb1225(41)      (Show Source): 
You can  put this solution on YOUR website! (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 
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