Question

Quadrilateral ABCD ​ is inscribed in this circle.

Answer 1

The answer to this is 65. 

Remember that the angles opposite of each other equal to 180. So a+c=180 and b+d=180. 

First, we solve for x. Since we know that b and d equal to 180, we subtract 148 from 180. 
180-148=32. x=32. 

Then we plug that in the expression for angle a. 
2x+1 becomes 2(32)+1
2*32=64
64+1=65.
a=65