# If x+y=10 and x+z=20 and y+z=24 then

what is x+y+z=?

X+Y=10

Y=10-X Use this to substitute for Y

X+Z=20

Z=20-X Use this to substitute for Z.

Y+Z=24 Substitute for Y and Z

(10-X)+(20-X)=24

30-2X=24

-2X=-6

X=3

X+Y=10 Put in value for X.

3+Y=10

Y=7

X+Z=20 Plug in value for X.

3+Z=20

Z=17

CHECK:

Y+Z=24

7+17=24

24=24

X+Y+Z=?

3+7+17=?

27=?

ANSWER: The sum X+Y+Z=27