Question

If the average of 9 and x is equal to the average of 7, 3, and x, what is the value of x?

Answer 1

Hello !

(9 + x)/2 = (7 + 3 + x)/3

3(9 + x) =2(7 + 3 + x)

27 + 3x = 14 + 6 + 2x

27 + 3x = 20 + 2x

27 - 20 = 2x - 3x

7 = -x

x = -7

you can check it works for the 2 averages