Explanation:
Well you got a good start. #16 = 105°, #17 = 27°, and #15 = 48°.
Inscribed angles are half the arc angle, so #3 = #10 = 21°, and #4 = #5 = 39°.
That means #14 = #12 = 120°, and #11 = #13 = 60°.
The sum of the angle arcs is 360°, and AD is the diameter, so it splits it in half. So arc BC is 180 - 78 - 42 = 60°, so #1 = 30°.
Therefore, #2 = 90°.
AG and FG are both radii, so AGF is an isosceles triangle. Therefore, #8 = #9 = 66°.
Similarly, FG and DG are both radii, so FGD is an isosceles triangle. So #6 = #7 = 24°.
That means #18 = 129°. So #20 = 129° and #19 = #21 = 51°.
That's all of them.