Question

If x+y = 6, y+z = 7, and z+x = 9, what is the average (arithmetic mean) of x, y, and z?

Answer 1

11/3 . . . or . . . 3 2/3

Explanation:

Adding the three equations will give 2x+2y+2z:

(x +y) +(y +z) +(z +x) = 6 +7 +9

2x +2y +2z = 22

Dividing by 2 gives the sum of three variables:

x +y +z = 11

The average of x, y, and z is their sum divided by 3:

(x +y +z)/3 = 11/3