Answer:
Step-by-step explanation:
Remark
The figure inside the circle is a quadralateral. The 4 angles touch the circumference of the circle. The figure is further defined as a cyclic quadrilateral.
One of the properties of such a figure, is that the opposite angles are supplementary. That is they add to 180.
Equation and solution
? + 100 = 180 Subtract 100 from both sides
? + 100 - 100 = 180 - 100
? = 80 degrees
Answer
? = 80
