Question

How do you simplify `(4y-9)-(3y+10)`?

Answer 1

`y - 19`

Explanation:

A place where students commonly make mistakes with is the terms after the subtraction sign, in this case `3y + 10`.

Pretend that there is a negative 1 in front of `(3y + 10)`. So you would have: `-1(3y + 10)`

Distribute that negative one to the terms in the parenthesis, to get `-1(3y) + -1(10) = -3y - 10`

Combine that with the remaining expression and then simplify.
`4y - 9 - 3y - 10`

Combine like terms:
`(4y - 3y) = y`
`(-9 - 10) = -19`

Put those together to get the answer of:
`y - 19`