Question

X-y=3.

2x+4y=12

X+y=4

Answer 1

$x = 3 + y \\ 2(3 + y) + 4y = 12 \\ 6 + 2y + 4y = 12 \\ 6y = 12 - 6 \\ y = \frac{6}{6} \\ y = 1 \\ \\ \\ x + y = 4 \\ x = 4 - 1 \\ x = 3$