A. 5

B. 7.5

C. 15

D. 12.25

Add both equations to get all variables together:

2x + y + y + 2z = 23 + 7

2x + 2y + 2z = 30

We can divide both sides by 2 to simplify:

(2x + 2y + 2z)/2= 30/2

x + y + z = 15

Notice: the average of x, y, and z is:

(x + y + z)/3

But x + y + z = 15, so we have:

15/3 =

**5, answer A**