SOLUTION: how can I solve this expression help please : 13- 3a for a = -1

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Question 9540: how can I solve this expression help please :
13- 3a for a = -1
Answer by thecampusnerd(13) (Show Source):
You can put this solution on YOUR website!
Alright, since a = -1, plug -1 in for "a".

Your equation will come out like this:

Now use your Order of Operations. Notice that the 3 has a minus sign in front of it. Because of that very minus sign, we're going to call it -3. Using the Order of Ops, you'll mulitiply -3 by -1, which is positive 3 (A negative times a negative equals a positive. The negatives cancel each other out.)

Because the 3 is now positive, you're going to change the expression from 13 - 3 to 13 + 3.

Do the math and you have your answer. 13 + 3 = 16.

Now, let's see it in the less wordy version...