Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'd like to take maths seriously but I'm not that great at it, so I decided to learn at home. I know this is pretty basic, but as I said, I'm pretty bad at maths, haha.

The worksheet gives me this example:

$7 (9o + 7) = 63o + 49$

I completed this one myself:

$5 (3l + 7) = 15l + 21$

My question is, what do I do if the plus operator is replaced with substraction?


$-3 (6w - 2)$

Here's what I got, although I doubt it's correct: $-18 w - -1.5$

Thanks kindly for your help!

share|cite|improve this question
It is far better to type $-18 w - (-1.5)$ than $-18 w - \, -1.5$ (-18 w - -1.5), because this last one is not a standard notation. – Américo Tavares Jan 12 '13 at 19:18
up vote 4 down vote accepted

For any $\;a,\,b\,:\;\;\; a - b = a + (-b).\;\;$

So for your last example, we can proceed as follows:

$$-3(6w - 2)\, = \,-3\,[\,6w + (-2)\,]\, =\,(-3)(6w) + (-3)(-2)\, = \,-18w + 6$$

share|cite|improve this answer

It's same, $-3(6w - 2) = (-3)(6w) + (-3)(-2) = -18w + 6$

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.