Two cars leave the same location traveling in opposite directions. one car leaves at 3: 00 p. m. traveling at an average rate of 55 miles per hour. the other car leaves at 4: 00 p. m. traveling at an average rate of 75 miles per hour. let x represent the number of hours after the first car leaves. how many hours after the first car leaves will the two cars be 380 miles apart?

equation:

hours; so i kinda got this down but if the 55mph leaves first it would take 6.9 (379.5 to be miles apart from car b) or 7 hours ( to be 385 miles apart from car b)
the thing is i dont have a exact hour that would make them 380 miles apart on the dot but i am close