Solve the system by elimination.
2x - 2y + 7z = 23
2x + y -2z = -5
31x - y - 7z = 0
The solution is ( , , , )
double the 2nd and add to the 1st to get:
6x + 3z = 13
add the 2nd and the 3rd to get:
33x - 9z = -5
You now have 2 equations in 2 variables,
you should be able to find x and z
once you have those two values sub into one of the originals
to get the y value
Hint: the z will be a whole number, the others are very simple fractions