Suppose you know that a car company charges a base rate and charges $2 a mile. If Joe drove 15 miles and the total cost of the rental was $50, how much was the base cost?

50 - (15 * 2) = ?

20?

Of course.

To find the base cost, we need to subtract the cost per mile from the total cost and then divide the result by the number of miles Joe drove.

Let's break down the calculation step by step:
1. Multiply the cost per mile by the number of miles driven: $2 * 15 miles = $30.
2. Subtract the result from the total cost to get the base cost: $50 - $30 = $20.

Therefore, the base cost of the rental is $20.