Ihave no clue how to do any of these problems so if anyone knows any an explanation would be nice.

#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.

What’s the question?