The y-intercept is the value of y when x = 0, here, y-intercept = 5.
It is the initial position of the turtle.
Average rate of change = y(4) - y(1) / 4 - 1 = 93 - 27 / 3 = 66/3 = 22
It represents the displacement per hour from the first hour to the fourth hour.
If it travelled at 22 miles per hour till it has travelled 225 miles, it must have travelled 225/22 = 10.2 hours.
Domain is 0 ≤ t ≤ 10.2