1315 все! Пожалуйста

1)                2)                       3) y-6x=-25x+y=9         3x+y=1                     y-x=-5 {;-1x-y=1           x+y=5  {:(-1)                                                               y-6x=-25                    3x+y=1                   -y+x=52x=10           -x-y=-5               x=5                                               -5x=-20                      2x=-4                         x=45+y=9             x=-2                          y-6*4=-25y=4                 3*(-2)+y=1                  y=-25+24                        -6+y=1                         y=-1                          y=7