9 is the answer.
How?
We need to find the total number of hours he worked for, and then we need to divide the amount of money he earned by the number of hours he worked for to find how much he earned per hour.
To find the total number of hours worked, add 2.75 and 1.75. The answer is 4.5 hours.
Divide 40.50 by 4.5, and the answer is 9. So, he earned 9 per hour.
