The answer is none. Since you have to add your a's first, your left with 0 meaning that there is no more a's meaning that you have no solution. Hope this helps!
In 4 hours they will be 400 miles apart 4 times 55 is 220 and 4 time 45 is 180 since there going in opposer directions add the miles together and it equals 400 so it takes 4 hours
