geometry

Opposite angles in an inscribed quadrilateral are supplementary

 

soooo     a-18 + a+16 = 180

                   a = 91

 

 

ALL of the angles sum to 360

 

a+16     + a+ 30   + a-18   + k = 360

91 + 16   + 91 +30   + 91 -18   + k = 360     solve for k