Question 802043
Substitution:

14. y=-3x+4
      -6x-2y=-8

16. x=y-1
      -x+y=-1

18. y=-3x+1
      2x+y=-4

20. 5x-y=5
       -x+3y=13

22. -5x+4y=20
       10x-8y=-40
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Is that all 1 problem?