In order to understand this question, one needs to understand the construction first. After creating POQ, Meg picks a radius r and makes a circle around O. There are 2 points where the circle meets the triangle. Then, she meets another radius and she makes a circle of radius s around each of the points on the triangle. The two circles cross at one point, as can be seen in the figure. Let's name the first two points A and B and let's name the last point S. We have that for the triangles OAS, OBS we have OA=OB=r, BS=AS=s and that OS is common to both. Thus by the S-S-S triangle equality theorem, the triangles are equal. Hence for the angles AOS=BOS, namely POS=QOS. Since POQ=POS+QOS, we have that POS has to be half of POQ. The only consistent choice is the third one, POS=20 degrees and POQ=40 degrees.
