Hello,
When we have a quadrilateral inscribed in a circle the opposite angles are supplementary.
Therefore, we can write and solve the following equation:
4x + 5 + x + 15 = 180
5x + 20 = 180
5x = 160
x = 32
Then, you substitute in 32 for x in the expression for A, you will have:
4(32) + 5
128 + 5
133
The measure of angle A is 133 degrees.
Good luck,
MrEQ