Hello,
When we have a quadrilateral inscribed in a circle, the opposite angles add up to 180 degrees (supplementary).
Therefore, we can write and solve the following equation first with angles B and D.
3x + 9 + 2x - 4 = 180
5x + 5 = 180
5x =175
x = 35
Then, sub 35 in the expression for angle A and you will get:
2(35) + 3
70 + 3
73
Angle A is 73, that would make angle C equal to 107 degrees, because 180 - 73 = 107.
Good luck,
MrEQ
