**QUICK AND EASY** ~Extra points~
(Picture has question)

I need help on this.. I knew the answer at one point but I forgot what it means now.. if you could add a little explanation with the answer, that would help so much! Thank youu <3

You are traveling in a car going at a constant speed of 100km/h down a long, straight highway. you pass another car going in the same direction which is traveling at a constant speed of 80km/h. as measured from your car's reference frame this other car is traveling at −20km/h. what is the acceleration of your car as measured from the other car's reference frame? what is the acceleration of the other car as measured from your car's reference frame?