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?

A) m+6

B) m+7

C) 2m+14

D) 3m+21

For this case we have to:

x = (m + 9) / 2

y = (2m + 15) / 2

z = (3m + 18) / 2

The average of x, y, and z is:

Average = (x + y + z) / 3

Average = (((m + 9) / 2) + ((2m + 15) / 2) + ((3m + 18) / 2)) / 3

Average = (((m + 9)) + ((2m + 15)) + ((3m + 18))) / 6

Average = (6m + 42) / 6

Average = (m + 7)

answer:

The average of x, y, and z in terms of m is

B) m+7