Решите медодом потстановки
{3x+4y=47
{2y-x=1

{2(x-2y)=x-8y{5(x+y)=2(x-y)+10{2x-4y=x-8y{5x+5y=2x-2y+10{2x-4y-x+8y=0{5x+5y-2x+2y=10{x+4y=0|*3{3x+7y=10-{3x+12y=0-{3x+7y=105y=10|:5y=23x+12*2=03x=-24|:3x=-8{3(x+4y)-4x=2(2x+y){7(x-5y)+6x=3(x+4y)+27{3x+12y-4x=4x+2y{7x-35y+6x=3x+12y+27{-x+12y-4x-2y=0{13x-35y-3x-12y=27{-5x+10y=0|*2{10x-47y=27+{-10x+20y=0+{10x-47y=27-27y=27|:(-27)y=-1-10x-1*20=0-10x=20|:(-10)x=-2{15+2(x+3y)=3(4x+y){2(5x-y)-3y=2+3(2x-y){15+2x+6y=12x+3y{10x-2y-3y=2+6x-3y{2x+6y-12x-3y=-15{10x-5y-6x+3y=2{-10x+3y=-15|*2{4x-2y=2|*3+{-20x+6y=-30+{12x-6y=6-8x=-24|:(-8)x=312*3-6y=6-6y=6-36-6y=-30|:(-6)y=5{5(7x+2y)-11y=6(2x+y)+2 {33+3(6x-5y)=3(x+2y)-5y{35x+10y-11y=12x+6y+2{33+18x-15y=3x+6y-5y{35x-y-12x-6y=2{18x-15y-3x-6y+5y=-33{23x-7y=2|*16{15x-16y=-33|*7-{368x-112y=32-{105x-112y=-231263x=263|:263x=115*1-16y=-33-16y=-33-15-16y=-48|:(-16)y=3