Option A (1,-7) is the correct solution.
2x-9 = y or 2x -y=9 ---------------(1)
7x-2y=21 -----------------------------(2)
on multiplying eq (1) by 2 we get:
4x - 2y = 18 -----------------------(3)
On subtracting eq(3) from eq(2) we get:
3x = 3
or x = 1
putting the value of x in eq 1 we get:
2(1) -9 = y
or y = -7