To find the average number of billboards per hour, we need to add up the total number of billboards seen and divide it by the number of hours.
In this case, the total number of billboards seen is 17 + 20 + 23 = 60 billboards.
Since there are 3 hours, we divide 60 by 3 to get an average of 20 billboards per hour.
So Benjamin should tell James that the average number of billboards they have seen per hour is 20.
#### 20
The answer is: 20
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
After counting 17 billboards in the first hour, 20 billboards in the second hour, and 23 billboards in the third hour, James asks Benjamin about the average number of billboards they have seen per hour. What should Benjamin tell him?

### Answer:
