Ok. Draw a right triangle. Say a is the distance of the car from the intersection. Say b is the distance of the truck from the intersection, and say c is the distance between the car and the truck. You know the equality Good. Now differentiate and see what you can plug in. You know everything here but c, and dc/dt (which you are solving for) You can use right triangles to solve for c at t=2, and then you should have you answer.