Answer:
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