10-4(2x+5)=6y-13
4y-63=5(4x-2y)+2
4y-63-20x+10y-2=0
14y-65-20x=0
x=0.7y-3.25
3-8x-6y=0
3-8*(0.7y-3.25)-6y=0
3-5.6y+26-6y=0
29-11.6y=0
y=29/11.6y=2.пятых
14*2.5-65-20x=0
-30-20x=0
x=-30/20
x=-1.5
а1+а5=20
а2+а3=17
a₁ + a₁ + 4d = 20
a₁ + d + a₁ + 2d = 17
2a₁ + 4d = 20
2a₁ + 3d = 17
a₁ + 2d = 10
a₁ = 10 - 2d
a₁ = 10 - 2d
2*(10 - 2d) + 3d = 17
20 - 4d + 3d = 17
- d = 17 - 20
- d = - 3
d = 3
a₁ = 10 - 2*3
a₁ = 4
ответ: a₁ = 4; d = 3