-2x + 3y = 14, (1) x + 2y = 7. (2) To solve this system, multiply the equation (2) by 2 and then add to the equation (1). In this way, you eliminate the unknown x and get a single equation for the unknown y: 3y + 4y = 14 + 2*7, or 7y = 28, y == 4. You just found y. Now substitute the value y = 4 into equation (2) and get x + 2*4 = 7. Hence x = 7 - 8 = -1.