maximize x_1 + 2x_2 - x_3
subject to
	-2x_1 - x_2 - x_3 >= -14
	4x_1 + 2x_2 + 3x_3 <= 28
	2x_1 + 5x_2 + 5x_3 <= 30

	x_1 >= 0
	x_2 >= 0
	x_3 >= 0