Let d(t) be the total number of miles Joanna has cycled, and let t represent the number of hours after stopping for a break during her ride.
d(t)=12t+20
So, d(4) = [32,96,88,68]. This means that after [cycling 4 miles, 4 hours, a 4 hour break, cycling at a speed at 4 mph], Joanna [took a 96 minute break, cycled for 68 miles total, rode for 32 hours total, cycled 88 miles total]