Respuesta :

2x + y = 4
2x - y = 8
-------------add
4x = 12
x = 12/4
x = 3

2x + y = 4
2(3) + y = 4
6 + y = 4
y = 4 - 6
y = -2

okay....so x = 3 and y = -2

3x - y = ?
3(3) - (-2) = ?
9 + 2 = 11....so ur answer is 11