We run a business that rents out canoes and kayaks. A canoe rental costs $9 per day, and a kayak rental costs $12 dollars per day. One day, our business rents out 4 canoes for every 3 kayaks and receives a total of $432 in revenue. How many more canoes than kayaks were rented out?  Choose the correct choice from the following choices:
A) 10 B) 9 C) 8 D) 7 E) 6

Rationale: "let x be the number of canoes . then 3 x / 4 is the number of kayaks . 9 x + ( 3 x / 4 ) * 12 = 432 9 x + 9 x = 432 18 x = 432 x = 24 ( canoes ) 3 x / 4 = 18 ( kayaks ) there were 24 - 18 = 6 more canoes rented out . the answer is e ."
Answer: E