Try this option: to define just substitute the coordinates into the equation of the line. For point (2;12), it means x=2; y=12: 12-5=5*2 ⇒ 7≠10; ⇒ (2;12) is not solution. for point (-2;-5), it means x=-2; y=-5: -5-5=-2*5; ⇒ -10=-10, ⇒ (-2;-5) is solution.