to make it easier to solve, think of it this way, point c and a are on the same "line",and point A is on the line under pi over 6. We know that pi over 12 is less than pi over 6, so that could potentially be the line that both points are on if that makes sense. We can also see that the real axis has the value of pi, and that point C is the value less than that. Also, point C is in the direction of where the negative "x values" would be
The graph of y > mx, where m > 0, consists of a dashed line and a shaded half plane. The line has a positive slope and passes through the origin. The shaded half plane is above the line.
You will pay $18 for a item with original price of $90 when discounted 80%. In this example, if you buy an item at $90 with 80% discount, you will pay 90 - 72 = 18 dollars.