Classify each system of equations as having a single solution, no solution, or infinite solutions. y = 11 − 2x 4x − y = 7 x = 12 − 3y 3x + 9y = 24 2x + y = 7 -6x = 3y − 21 x + y = 15 2x − y = 15 2x + y = 7 -4x = 2y + 14 x + 4y = 6 2x = 12 − 8y