A: number of nonfiction books
b: number of fiction books
a+b=2000
a=3b
b=500
a=1500
Cubed means you have to multiply it by the other number like an exponent so that means the answer is z3
If the tax was 7 cents then each bottle would cost 1.06 each, because tax doesn't mean it's three dollars plus tax which comes to 3.07, it's that if you have a water bottle coming out to 99 cents each and the tax was 7 cents, you add 7 to 99. Which in money, comes out to 1.06 each bottle. So the total bill is 3.18.
I hope this helped! I don't wanna get your answer wrong! >o<
