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-7(1-4m)= 13(2m-3)

Basic Algebra

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3 Answers

-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!

-7+28m=26m-39 Add 39 to both sides 32+28m=26m Then subtract 28m from both sides 32=-2m Then divide both sides by -2 -16=m