31. What is the solution to the system of equations? - 7x-2y+z=-2 6x-y-z=-18 5x+4y-z=18

x = - 1, y = 7, z = 5

-7 - 2 - 1 - 2 6 - 1 - 1 - 18 5 4 - 1 18

use 2. - 3.

= - 1 - 5 0 - 36 - - - 4.

use 1. + 2.

= - 1 - 3 0 - 20 - - - 5.

use 4. + 5.

= 0 - 8 0 - 56

=> y = 7

y = 7 back into 5.:

x - 35 = - 36

=> x = - 1

x = - 1 and y = 7 back into 1.:

7 - 14 + z = - 2

=> z = 5