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 am refreshing algebra to get ready for calculus and i have a problem and my book doesn't explain it well.

take this equation simplification

-15(x/3) = -5 * 3 * (x * 1/3)

Now, when i distribute the 3 to eliminate the parens, i get

-5 * 3x * 1 = -5 * 3x

the book says thats wrong,

how do you get -5x for the answer? im missing something

share|cite|improve this question

The 3s cancel on the rhs. You multiplied by 9. $$\frac{(-5)(3)(x)}{3}=-5x$$

share|cite|improve this answer

You are trying to distribute as if it were an addition not a product. So $5*3*(x*1/3) = 5*3*x*1/3 = 5x$. what you're doing is multiplying 3 by x and 1/3.

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.