1. quadrilateral abcd is inscribed in this circle.
what is the measure of angle b?

2. quadrilateral abcd is inscribed in this circle.
what is the measure of angle a?

3. quadrilateral abcd is inscribed in this circle.
what is the measure of angle c?

1) The opposite angles of a inscribed quadrilateral are supplementary.

3x - 12 + x = 180
4x - 12 = 180 
4x = 192
x = 48

Now we know the value of x we can substitute it for x in the expression of angle B.

3(48) - 12 = 132

Angle B is 132°

2) The opposite angle of an inscribed quadrilateral are supplementary. So first we will find the value of x.

28 + x = 180
x = 152

The value of x is 152 so we can substitute this in for x in the expression of angle A.

152 - 36 = 116

So angle A is 116°

3) To find the measure of angle C we will first find the value of x.

3x + 9 + 2x - 4 = 180
5x + 5 = 180
5x = 175
x = 35

Now we can find the value of angle A an then subtract it by 180 for angle C.

2(35) + 3 = 73

180 - 73 = Angle C 
107 = Angle C