The meaning of a quadrilateral inscribed in a circle is that the angles on the opposite vertices are supplementary or in other words equals to 180 degrees.
In this exercise it is asked you to find the measure in degrees of angle A. First of all, you have to find the value of x. To do this you have to select two angles, on this case angles B and D.
m<B+m<D=180 Substitute the given values of angles B and D
28+x=180 Subtract in both sides by 28
x=152
Now that the value of x is known, you can substitute it into the expression representing angle A.
m<A=x-36
m<A=152-36
m<A=116
The measure of angle A is 116 degrees.
