If x is the average (arithmetic mean) of m and 9, y is the average of 2m and 15, and z is the average of 3m and 18, what is the average of x, y, and z in terms of m?

Question: If x is the average (arithmetic mean) of m and 9,y is the average of 2m and 15, and z is the average of 3m and 18, what is the average of x, y, and z in terms of m?

Solution:
Given that,
x is the average of m and 9.
x = (m + 9)/2

y is the average of 2m and 15.
y = (2m + 15)/2

z is the average of 3m and 18.
z = (3m + 18)/2

Now, x, y, z- average of-
= (x + y + z)/3
= [(m + 9)/2 + (2m + 15)/2 + (3m + 18)/2]/3
= [(m + 9 + 2m + 15 + 3m + 18)/2]/3
= [(6m + 42)/2]/3
= (3m + 21)/3
= m + 7

Correct answer should be: খ) m + 7