bridge

If car X followed car Y across a certain bridge that is 1/2 mile long, how many seconds did it take car X to travel across the bridge?
(1) Car X drove onto the bridge exactly 3 seconds after car Y drove onto the bridge and drove off the bridge exactly 2 seconds after car Y drove
off the bridge.
(2) Car Y traveled across the bridge at a constant speed of 30 miles per hour.