A) need a complete answer for the first picture. b) answer is shown as already correct. As seen in the second picture, but need an easier way to answer it.

a) The angle ABC measures 90° as the triangle in the circle is an RHS one

b) The measure of angle DEF is half of the given angle as the angle DOF's midpoint bisects the latter angle

Hope it helps :)

astronomers is your final answer! : )