You don't need help. You know the formula: Distance = (speed) x (time)
The formula is always true, for any distance, speed, and time.
Plug in the numbers you know: 120 miles = (speed) x (1.5 hours)
Divide each side by "1.5 hours": (120 mi / 1.5 hr) = speed
Doo-da division: 120/1.5 mi/hr = speed
Clean it up: 80 miles/hour = speed
