Going against the current, a boat takes 6 hours to make a 120-mile trip. when the boat travels with the current on the return trip, it takes 5 hours. if x = the rate of the boat in still water and y = the rate of the current, which of the following systems could be used to solve the problem? 6(x - y) = 120 and 5(x + y) = 120 6(x + y) = 120 and 5(x - y) = 120 6x - 5y = 120 and x + y = 120