Б...................................
3x+1=2x-8y-5
2x+8y+9=10y+15
x+8y=-6
2x-2y=6 :2
x-y=3
вычитаем
9y=-9
y=-1
x+1=3
x=2
у (-2,5)= 4*(-2,5)- 30=-10-30=-40