Question

How do you solve `-21=y-4`?

Answer 1

`-17=y`

Explanation:

One way to work this type of question is to remember that if we do one thing to one side of an equation, we need to do the same thing to the other side in order to not change the balance. For instance, I can say this:

`6-2=4`

and this

`6-2color(blue)(+3)=4color(blue)(+3)`

I added 3 to both sides and the equation balance still holds.

Now to our question.

If we add 4 to both sides, we'll have `y` alone on one side and what it's equal to on the other:

`-21color(blue)(+4)=y-4color(blue)(+4)`

`-17=y`