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