1. If the front of the red car is used as a reference point, how far away is the white van?

-26 m

Explanation:

In the image, the original reference point is the front of the black car which is at point 0 meters. The red car is 15 m from the black car while the white van is -21 meters from the black car. If the front of the red car is used as the reference point then the black car would be -15 m from the red car and the white van would be -21 m from the black car, therefore:

Distance of white van from the red car (reference point) = Distance from red car to black car + distance from black car to white van = -15 m + (-21 m)

Distance of white van from the red car (reference point) = -15 m -21 m = -36 m