Answer:
d = 6 km
Step-by-step explanation:
The total cost of a ride includes a fixed, up-front cost and a variable cost:
C(x) = $5.00 + ($2.50/km)x, where x is the number of kilometers covered.
Setting C(x) = $20, we get:
$20 = $5 + ($2.50/km)x
which needs to be solved for x:
$15 = ($2.50/km)x
Dividing both sides by ($2.50/km) yields
6 km = d