Final answer:
To find the average, add the numbers and divide by the total number of numbers.
Step-by-step explanation:
To find the average of the given numbers, you need to add them together and then divide the sum by the total number of numbers. So, for the given numbers: $39, $75, $54, $40, the sum is $39 + $75 + $54 + $40 = $208. Now, divide this sum by 4 (since there are 4 numbers) to get the average: $208 ÷ 4 = $52.
Therefore, the average of the numbers $39, $75, $54, $40 is $52.