Let F = the sum of the 15 numbers that don't include k and m

So, the average of the 15 numbers \(= \frac{F}{15}\)

The average (arithmetic mean) of 17 numbers is j.
We can write: \(\frac{F + k + m}{17} = j\)

What is the average of the remaining 15 numbers in terms of j, k and m?

Take: \(\frac{F + k + m}{17} = j\)

Multiply both sides of the equation by 17 to get: \(F + k + m= 17j\)

Subtract k and m from both sides: \(F= 17j - k - m\)

Divide both sides by 15: \(\frac{F}{15}= \frac{17j - k - m}{15}\)

Answer: D