#1). The length of the whole circumference is (π · D) = 12π .
120° is 1/3 of 360°, so arc-AB is 1/3 of the whole circumference.
#2). 60° is 1/6 of 360°.
So arc-CD is 1/6 of the whole circumference (which is given).
#3). The circumference of the circle is (π·D) = 20π .
70° is (70°/360°) of the whole circle, so arc-XY
is (70/360) of the whole circumference.
#4). Sorry, I don't remember anything right now about
angles between chords.
I hope what I've given you so far is worth 5 points.