These aren't that hard--especially once you've done the first 13 questions. There are many 45-45-90 triangles in there.
14. ∠BCO = 45°
15. ∠GOF = 45°
16. ∠OFG = 45°
17. ∠GFH = 180° - ∠JFH = 58°
18. ∠FGH = 90°
19. ∠EFJ = 45°
20. ∠GOC = 180° (the points are collinear)
