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.

Cant understand the first statement!