First we have to determine a linear equation. We will take two points (0,900) and (1,850):
y=mx+b
900=m*0+b, b=900
850=m*1+900
m=-50
Linear equation is:
y=-50x+900
Part A: y-interception is
y=900 or(0,900).
It means that a car has to travel a distance of 900 miles to reach a final destination.
Part B:Average rate of change:

=
-50. It represents how many miles per one hour changes the distance from a destination.
Part C: Domain of this function if the car traveled the same rate until it reached its destination:
0=-50x+900
50x=900
x=900/50=18
Domain:
x∈ [0, 18].