Question

{2х+у=20
{Х-3у=-1
Решите систему уравнений

Answer 1

2x+y=20
x-3y=-1

x=3y-1
2(3y-1)+y=20

x=3y-1
6y-1+y=20

x=3y-1
7y=21

x=3y-1
y=3

x=3*3-1
y=3

x=9-1
y=3

x=8
y=3