Pls look at attached picture i have tried asking many and no one can explain it

measure of arc ABC = 283°

Step-by-step explanation:

First we have to find y

7y - 7 + 4y + 6 +20y - 11 = 360

31y - 12 = 360

31y = 372

y = 12

Since all the angles are central angles and intercepted arcs of those angles have the same measure,

the measure of arc ABC  = 4y + 6 + 20y - 11

                                         = 24y - 5

                                         = 24(12) - 5

                                         = 283