We are given the average age of the 40 members of the computer science camp is 17 years.
We are also given that there are X girls, 15 boys, and 5 adults.
The average age of the girls is 15 and the average age of the boys is 16.
To find the average age of the adults, we can use the concept of weighted averages.
The total age of the girls is X * 15.
The total age of the boys is 15 * 16.
The total age of the adults is 5 * average age of adults.
The total age of all the members of the camp is (40 * 17).
We can set up an equation using the given information:
(X * 15) + (15 * 16) + (5 * average age of adults) = (40 * 17)
Simplifying, we have:
15X + 240 + 5 * average age of adults = 680
15X + 5 * average age of adults = 440
We are given that the average age of the adults is 28, so we can substitute it into the equation:
15X + 5 * 28 = 440
15X + 140 = 440
Subtracting 140 from both sides of the equation, we find:
15X = 300
Dividing both sides of the equation by 15, we get:
X = 20
The value of X is 20.
The answer is: 20
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
The average age of the 40 members of a computer science camp is 17 years. There are X girls, 15 boys, and 5 adults. If the average age of the girls is 15 and the average age of the boys is 16, what is the average age of the adults?
If we know the answer to the above question is 28, what is the value of unknown variable X?

### Answer:
