during a long trip, billy stops at a rest stop to have a snack. just as he starts to eat, he sees a bus pass by. after he eats three donuts, billy sees a motorcycle pass, and after three more donuts, billy sees a car pass. while billy is snacking, molly is further down the highway taking a break at a different rest stop. just as she starts to eat, she sees the bus pass by. after she eats three muffins, molly sees the car pass, and after three more muffins, molly sees the motorcycle pass. billy and molly eat at the same constant rate. find the speed of the bus if the car travels 60 km/h and the motorcycle travels 30 km/h.
