Genevieve is buying a car audio system that consists of a stereo, speakers, and amplifiers. she is choosing between 5 types of stereos and 2 types of amplifiers. if she has a total of 30 choices, how many types of speakers must there be?
a.3
b.6
c.10
d.20

The answer is A.

The total choices are calculated by the product of the options in each case.

here she has 5 types of stereos and 2 types of amplifiers, with this two items genevieve gets 10 combinations.

If we also add the speakers, let's suppose we get x options for the speakers, and the problem says that the total options are 30, so 10*x = 30

dividing by 10, we get x = 3.

so there are 3 options for speakers, and the correct answer is A.