The condition for consistency is
For c = 0, the three equations are
2x + 2y = 3; 2x + 4y = 6; 4x + 16y = 36
and the solution is x = -3; y = 3.
For c = -10, the equations are
2x + 3y = 3
- 8x - 6y = -4 ⇒ 4x + 3y = 2
64x - 36y = 16 ⇒ 16x + 9y = 4
and the corresponding solution is x= 1/2,;y = 4/3.