math
posted by Pablo .
At a certain grocery store, "a" customers each spend an average of $30 every "b" hours. How much revenue , in dollars, does the store collect in "c" hours?

30ab = c

c hours * a cust/hr * $30/b cust = 30ac/b $
check:
If 10 customers spend $300 in 5 hours, that's $60/hr, so in 3 hours that would be $180.
30ac/b = 30*10*3/5 = 180 
I also came to that answer, but it isn't one of the choices. The choices are:
(A) 30c/ab
(B) bc/30a
(C) 30bc/a
(D) 30ac/b
(E) 30b/ac 
thanks Steve!

Steve's answer is right and is one of your choices.
Sorry  my answer is wrong.