3x − y − 2z=21 2x + y − 2z = 17 x + 3y − z = 11

I have literally tried this problem 6 times and can not get it right.
in order of operations by

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1 Answer

Call the equations A, B and C in order. A+B=D: 5x-4z=38.  This eliminates y; now we need to use C with A or B to eliminate y again: 3A+C=E: 10x-7z=74. E-2D=F: z=-2, so 5x=38+4z=30, making x=6. From B, y=17-2x+2z=17-12-4=1. Solution: (x,y,z)=(6,1,-2).

CHECK: A: 18-1+4=21; 12+1+4=17; 6+3+2=11. All OK.

by Top Rated User (1.2m points)

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