From line [1], we get y = -x + 3. We substitute this for y in line [2]:
3x - 2(-x + 3) = 14
This gives us: 3x + 2x − 6 = 14
So x = 4 and using line [1] we get y = -1.
Check in line [2]: 3(4) − 2(-1) = 14
So our solution (4, -1) is correct.