Lois P. answered • 09/18/12

Miss Lois -- Elementary School Tutor

Great answer, Natalee. I would only add that you are combining steps in your answer, which confuses many of my students when they first begin this type of problem.

The rule is you must keep the equation balanced, so the math your perform on one side of the = must also be done on the other side.

So, the long way looks like this:

2x + 5 - 7x = 15

subtract 5 from both sides

2x + 5 - 5 - 7x = 15 - 5

2x + 0 - 7x = 10

2x - 7x = 10

combine like with like:

2x - 7x = 10

-5x = 10

divide both sides by -5

-5x/-5 = 10/-5

x = -2