Question

Плиз помогите, решите подстановкой {x+y=7
{X-y=1

Answer 1

x+y=7 → x=7-y
x-y=1 → (7-y)-y=1

7-y-y=1 x=7-3
7-2y=1 x=4
-2y=1-7
-2y=-6
y=3

x=4, y=3