1. Pick a letter to eliminate and two equations that contain it to
   eliminate it from.

I will pick y to eliminate, and the first two equations to eliminate it
from:



Add corresponding terms and the y's drop out:



Since all the coefficients are equal, do let's divide every term by 2



2. Eliminate the same letter, y, from two equations that contain it to
   eliminate it, but this time use the equation that you haven't used
   yet

I will eliminate y from the second and third equations to eliminate it
from:



Add corresponding terms and the y's also drop out:



Now we have two equations in two unknowns



I will eliminate z by multiplying the first equation by -2:



Add them term by term and the z's drop out:



Substitute -1 for x in one of those equations, say









Now substitute -4 for z and -1 for x in one of the
original equations, say this one











So the solution is

(x,y,z) = (-1,4,-4}}}

Edwin