3(x+y)+(x-y)=20
3x+3y+x-y=20
4x+2y=20
4x=20-2y
x=5-1/2y
5(x+y)-(x-y)=28
5x+5y+x-y=28
4x+6y=28
4x=28-6y
x=7-3/2y
3(x+y)+(x-y)=20
3x+3y+x-y=20
4x+2y=20
4x=20-2y
x=5-1/2y
5(x+y)-(x-y)=28
5x+5y+x-y=28
4x+6y=28
4x=28-6y
x=7-3/2y
Пошаговое объяснение: