The speed of car A is 72.2 km/h while the speed of car B is 53 km/h. If car B is now 48 km ahead of car A, how much time is needed for car A to catch up with car B? car A let x = the current position of car A speed = 72.2 km/h time = x/72.2 hours car B let x + 48 = the current position of car B speed = 53 km/h time = (x + 48)/53 hours so, both cars will have travelled for the same amount of time when car A catches up with car B. then, x/72.2 = (x + 48)/53 solving for x gives x = -180.5 km thus, time of car A is -2.5 hours. You cannot have negative time. Could someone explain my solution? Thanks.