2x+5-7x=15

Question

multistep equation

Answer 1

2x+5-7x = 15 subtract 5 from both sides

2x -7x = 10

combine the x terms

-5x = 10

divide both sides by -5

x = 10/-5 = -2

x=-2

check the answer. replace x by -2 in the original equation

2x + 5 -7x = 15

2(-2) + 5 -7(-2) = 15

-4 +5 +14 = 15

1+ 14 = 15

15 = 15

Answer 2

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

 

Answer 3

We need to isolate x

2x + 5 - 7x = 15      (subtract 5 from left equation and add to the right equation)

2x - 7x = 15 - 5      (add up both sides)

-5x = 10                (divide both sides by -5 to isolate x)

x = -2

plug -2 back into original equation to check answer

2(-2) + 5 - 7(-2) = 15

-4 + 5 + 14 = 15

15 = 15