Im trying to help my daughter and we are lacking information like a formula for relative velocity.. here is one of 20 problems and I am wishing someone could explain it enough that we can learn and do the rest. Thanks

Two cars are traveling inthe same direction. Car A is traveling 62mph. Car B is traveling 70mph. When car B passes car A, how fast does car b appear to be going to the passengers in car A? How much slower does car A appear to be going to the passengers of car B?