Since z is already eliminated from the 2nd equation,
let's eliminate z from the 1st and 3rd equations:

Multiply the first equation by 3 and the 3rd equation by 5,
so the coefficients of z will be alike with opposite signs:



Add the equations term by term and the 15z and the -15z will cancel:



Put that with the original 2nd equation:



Add those term by term, the 4x and the -4x will cancel:



Substitute 3 for y in 









Substitute -1/2 for x and 3 for y in 2x-4y+5z=-33








(x,y,z) = (-1/2,3,-4}}}

Edwin