Let's say that they both start at a point A. If Bill travels south 45 miles in hour and Landin drives 30 miles north in one hour, after one hour, Bill is going to be 45 miles lower than point A and Landin will be 30 miles above point A, so they will be 45 + 30 = 75 miles apart. After two hours, they will be another 75 miles apart, so they will be a total of 75 + 75 = 150 miles apart. After 3 hours, they will be another 75 miles apart, so they will be a total of 150 + 75 = 225 miles apart.
