Question

How do you solve `9y-4(y+5)=40`?

Answer 1

This equation has one variable `(y)`; also called an unknown.

Solving this equation means to find all the real values that `y` can assume.

Explanation:

Here are the steps that you can follow to get the value(s) of `y`:

`"Step 1 :"` Open the brackets.

This means the you multiply the number outside the brakets`(color(red)(-4))` by every terms that's in the brackets : `(color(red)y` and `color(red)5)`

So, `-4(y+5)` becomes `-4*y+(-4)*5color(orange)=-4y-20`

Now we can write `9y-4(y+5)=40" "` as `" "9ycolor(orange)(-4y-20)=40`
`=>5y-20=40`

• Why is `9y-4y=5y`?
• Answer : Compare `9y-4y` to "nine yens minus four yens". The result is five yens. It's the exact same thing.

`"Step 2 :"` Group similar terms together.

Add `20` on both sides.
Result : `5y-20+20=40+20`
`=>5y=60`

`"Step 3 :"` Nos that you have grouped the like the terms. Make `y` to be alone on one side.

Divide both sides by `5`

Result : `(5y)/5=60/5`

`=>color(blue)(y=12)`