The complete circumference is given by the following equation:
(4y + 6) + (7y-7) + (20y-11) = 360
Rewriting we have:
31y - 12 = 360
Clearing and we have:
31y = 360 + 12
y = 372/31
y = 12
Then, the measure of the ABC arc is:
(4y + 6) + (20y-11)
= (4*(12)+6) + (20*(12)-11)
= 283 degrees
Answer:
283 degrees