Question

a) {x +y=5
{x - y = 1

Answer 1

2x = 6
x = 6/2
x = 3

substitui : 3 + y = 5
y = 5 - 3
y = 2

Answer 2

2x=6
x=6/2
x=3
x+y=5
3+y=5
y=5-3
y=2
S={3,2}