On a certain farm the ratio of horses to cows is 5:1. If the farm were to sell 15 horses and buy 15 cows, the ratio of horses to cows would then be 17:7. After the transaction, how many more horses than cows would the farm own?  Choose the correct choice from the following choices
A) 30	B) 40	C) 50	D) 60	E) 70
Originally, there were 5k horses and k cows.   7(5k-15) = 17(k+15)   35k-17k = 255+105   18k = 360   k = 20   The difference between horses and cows is (5k-15)-(k+15) = 4k-30 = 50   The answer is 50.
<result>C</result>
On a certain farm the ratio of horses to cows is 5:1. If the farm were to sell 15 horses and buy 15 cows, the ratio of horses to cows would then be 17:7. After the transaction, how many more horses than cows would the farm own?