Alex rode a bike 60 miles in 4 hours. For 5 minutes of the ride, he rode at 12 miles per hour. Which number related to Alex's bike ride represents a constant rate of change?

12 miles per hour

Step-by-step explanation:

The number 60 miles in 4 hours represents a rate of change of 15 mph, but the problem statement tells you Alex's speed was not constant at that value. (His speed was sometimes 12 mph, which is less than 15 mph. That also means at other times Alex's speed had to be more than 15 mph.)

The number 12 mph represents a constant speed (rate of change). The problem statement implies that Alex rode at that constant speed for 5 minutes, so that rate of change was truly constant (for that period).