You want to arrive at your friend's house by 5pm her house is 240 kilometers away if your average speed will be 80km on the trip when do you need to leave your house in order to get to her house in time
you must leave your house by 2:00 pm. what you do is you take your total distance and divide that by speed so in this case it is 240km / 80kmh = 3 hours meaning you have to leave the house by 2:00 pm
