Cheryl N. answered • 03/31/13
Certified; experienced with learning-different and advanced students!
-7(1-4m) = 13(2m-3)
The first thing you want to do it get rid of those parenthesis. You can do this by distributing the -7 and the 13. That means multiplying the -7 by each term inside it's parenthesis (the 1 and the -4m), and doing the same with the 13 on its side:
-7 + 28m = 26m - 39
Now the parenthesis are gone, so life is simpler. Next, you want to get all the 'm's on one side of the equation - I'm going to choose the left side, randomly. We can get the 26m on the left by subtracting 26m from both sides:
-7 + 28m - 26m = 26m - 39 - 26m
-7 + 2m = -39
Next, you want to get m by itself. That means you have to get the -7 and the 2 off of it. When you're solving for a variable, like now, you're going to use "reverse order of operations". Remember learning PEMDAS? Going in reverse order, addition and subtraction come first, so we need to get rid of the -7, because it's connected to the m by addition. It's a NEGATIVE 7, so we're going to ADD to get rid of it:
-7 + 7 + 2m = -39 + 7
2m = -32
We're still trying to get m by itself, so next we have to get rid of the 2. The 2 is being MULTIPLIED by m, so we're going to do the opposite, and DIVIDE to get rid of it. Remember, whatever you do to one side, you do to the other:
2m / 2 = -32 / 2
m = -16
You're done!
One problem you might have had with this question is keeping all the negatives straight. Remember that a negative is attached to the number on the RIGHT, and a negative times a negative is a positive!
