The line 6x - 2y = 12 goes through -6 on the y-axis and 2 on the x-axis ie through (0, -6) and (2, 0) The line will be solid and shaded above (towards the origin)
There are an infinite number of choices for the example points! Here is my selection. (0, 0) is in the solution set. 6 x 0 - 2 x 0 = 0 which is less than 12 (5, 0) is not in the solution set. 6 x 5 - 2 x 0 = 30 which is greater than 12 (2, 0) is on the line. 6 x 2 - 2 x 0 = 12
This result is actually true for any exterior angle. The exterior angle of a triangle is equal to the sum of the two remote angles, and above is a short proof of it.