7y+5-3y=-31

Question

what is y?

Answer 1

Hi, Victoria.

Y is a variable which serves as a placeholder for some number. To find y, or solve the equation, we want to get the variable by itself on one side of the equation. Just as a reminder, 7y means 7 times y. When we have a number and a variable next to each other, we don't need to write the multiplication sign.

In this problem, you have two terms with y, so you can combine them. 7y and -3y = 4y, so:

4y + 5 = -31            

We then want to "undo" what is being done to y; that is, do the opposite operation. Whatever you do on one side of the equation, you have to do the other side to keep it in balance. Subtract 5 from both sides:

4y + 5 = -31
    - 5     - 5
4y      = -36              Now divide both sides by 4

4y = -36
4       4

y = -9

You can plug -9 into the original equation to make sure it works:

7(-9) + 5 - 3(-9) =

-63 + 5 + 27 = -31         so it works.

Hope this helps!

Answer 2

     7y + 5 - 3y = -31

Combine like terms (7y and -3y) on the left side of the equation:

     (7y - 3y) + 5 = -31

      4y + 5 = -31

Subtract 5 from both sides of the equation:

      4y + 5 - 5 = -31 - 5 

      4y = -36

Divide both sides of the equation by 4:

      (4y) / 4 = (-36) / 4 

          y = -9