1. which of the given systems is a system of linear inequalities in two variables

a. 2x + y = 15 b. 3x - 2y ≤ 6
3x - y > 5 4x + y > 11

c. 2xy ≥ 14 d. 5x - 2y ≥ 10
7x - 2y < 8 2a + 7b > 6​