Question 1126612
Not a complete solution - just a possible way to use few steps -


{{{system(3x+4y+5z=18,2x-y+8z=13,5x-2y+7z=20)}}}



4*E2+E1 to eliminate y
and
-2E2+E3 to eliminate y


{{{system(4x+9z=90,x+9z=-6)}}}



E1-E2 to eliminate z

{{{3x=96}}}

{{{highlight(x=32)}}}-------one of the variables now found.


Use either equation from previous system to get y and z.


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{{{system(y=155/9,z=-38/9)}}}