Question

x+y =6 ,y+z=7, and z+x=9 the average of x y and z

Answer 1

x+y=6..............(1)

y+z=7.............(2)

x+z=9............(3)

Now showing you a trick

Add 1 ,2 and 3

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

==>2x+2y+2z=22

==>(x+y+z)=11.............(4)

Average of x,y,z is (x+y+z)/3

Divide (4) by 3

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

The average is 11/3

Hope it helps you.

Answer 2

Add the three equations

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

X+y+y+z+z+X=22

2x+2y+2z=22

2(X+y+z)=22

X+y+z=22/2

X+y+z=11

Average of X,y and z= sum of X y z divided by 3

X+y+z/3

11/3=3.66