Answer:
8
Explanation:
All angles of a quadrilateral and/or circle sum up to 360°. We can find the missing angle by subtracting 84, 84, and 100 from 360 to get 92 (imagine it in the blank area of the circle where there is no measurement).
12x is the inscribed angle of 92 and 100, which is 192. As we know, inscribed angles are 1/2 of their central angle.
1/2(192) = 12x
96 = 12x
x = 8
You can substitute the values to check: 12(8) = 192