# Math Help - How to combine this problem

1. ## How to combine this problem

I am doing homework on Combine Like terms. But I came to a problem that i just need to know the "how to" on this one.

-2n - (9 - 10n)

Now the answer is 8n - 9

I got at first -12n - 9

Can someone just explain the proper steps for this problem?

2. ## Re: How to combine this problem

Originally Posted by queequeeg
I am doing homework on Combine Like terms. But I came to a problem that i just need to know the "how to" on this one.

-2n - (9 - 10n)

Now the answer is 8n - 9

I got at first -12n - 9

Can someone just explain the proper steps for this problem?
$-2n-(9-10n)=-2n-(+9)-(-10n)=-2n-9+10n=(-2n+10n)-9=8n-9$

3. ## Re: How to combine this problem

Remember that two negatives equals a positive. The "-10" is negative, so when you subtract from a negative 10 you get positive 10.