Solve the following system of equations:

(1) 6x + 9y = -9
4x + 7y = -11

(2) 8x + 2y = 54
9x + 5y = 36

(3) 3x + 3y = -30
7x + 8y = -77

(4) 5x + 6y = 22
2x + 4y = 12

(5) 2x + 5y = 11
7x + 7y = -14

(6) 8x + 9y = 23
6x + 2y = -16

(7) 5x + 4y = -16
4x + 6y = -10

(8) 3x + 8y = 69
9x + 3y = 18

(9) 6x + 2y = 18
2x + 7y = -51

(10) 9x + 6y = -15
8x + 4y = -16