6x + y = 30 5x − y = 14
5a + 2b = 54 4a + b = 36
8x + 3y = 47 3x − y = 24
9x + y = 50 7x − y = 78
5a + 3b = 18 4a − 5b = 44
7x + y = 67 5x + y = 45
11x + y = 90 8x + 7y = 78
12x + 4y = 84 7x + 2y = 56