Tasks like this one are difficult for me. I have been looking at this task alone for a few hours now.
g) The circle has the center at O. AB cuts of a 60 degrees section, while DE cuts of a 20 degree section.
The rest is just like this; bestem = find. Vis at = show that.
The only thing I see is that $\angle AOB$ is $60^\circ$ And from that there is a rule that should make $\angle ADB = 30^\circ$ But I'm not convinced that is correct. I can't find a word for that rule in english. Wiki gets complicated really fast about even simple stuff.