What is 5 × 5

What is 5 − 5

Ben is planning a road trip with his friends. They start their journey with a full tank of gas, which can travel a distance of 400 miles. Along the way, they encounter several gas stations at different distances from their starting point. At the first gas station, Ben refills the tank with 15 gallons of gas. From that point, they can travel 20 miles per gallon. However, at the second gas station, Ben realizes that he forgot his wallet and cannot purchase any more gas. They are now 100 miles away from their destination. If Ben's friends decide to walk the remaining distance while Ben drives alone at a constant speed, how fast (in miles per hour) must Ben drive to reach their destination at the same time as his friends? Note: Assume Ben's friends walk at an average speed of 4 miles per hour.