To calculate the average speed of the bus, we need to divide the total distance traveled by the time taken. First, let's convert the time from hours and minutes to hours. We have 1 hour and 30 minutes, which is equivalent to 1.5 hours. Next, we can use the formula: average speed = total distance / time taken. In this case, the total distance is 42 miles and the time taken is 1.5 hours. So, the average speed of the bus is: 42 miles / 1.5 hours = 28 miles per hour (mph) Therefore, the average speed of the bus is 28 mph.