Question

x - y = 1,
x + 2y = 7;​

Answer 1

x - y = 1,

x=1+2=3

y=3-1=2

3-2=1

1=1

х+2у=7

х+2*(1-3х) =7

-5х=5

х=-1

y=4

-1+2•4=7

7=7

Как-то так...