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. so, d(4) = . this means that after , joanna .

For this case what you should know is that you have a function that depends on time.  the function represents the distance traveled by joanna.  we have then that d (4) means the distance traveled by joanna after having cycled for about 4 hours.  answer  after stopping for a break during her ride, joanna has cycled for 4 hours (d (4))

The simple function determines the number of miles joanna has ridden based on how many hours she was riding. for example, d(4) = 40. this means that after four hours, joanna has ridden 40 miles. this would also show that her speed averaged out to 10 miles per hour.

Ummm ok. for informing us