In a circle, the degree measure of an arc is the same as the measure of the central angle that intercepts it.
A full circle is 360 degrees.
Add all the measures and set equal to 360 degrees.
One angle measure is not given, but that angle has a mark and another angle has the same mark, so the angle whose measure is not give also measures -9x - 3.
-9x - 3 + x + 107 + (-6x + 8) + (-9x - 3) + (-13x - 1) = 360
-9x - 3 + x + 107 - 6x + 8 - 9x - 3 - 13x - 1 = 360
-36x + 108 = 360
-36x = 252
x = 252/(-36)
x = -7
