Question 38366
It is a bit difficult to explain the entire procedure, but in essence what you do is to eliminate the same variable from pairs of equations, via the linear combination method.  You want to "boil" three equations and three unknowns down to two equations and two unknowns...for example, from

x-2y+z =7
2x-5y+2z =17
-3x+7y+5z =-32
we can double the first equation and subtract it from the second one, eliminating x...repeat that procedure with the first and third equation, etc...
You will find the solution
x = 2, y = -3, and z = -1