What is m ∠DEC if measure of Arc DC = 150° and measure of Arc AB = 90°?A. 150°B. 120°C. 240°D. 90°

we know that
Inner angle, has its center at an inner point of the circle.
The measure of the interior angle is the half-summit of the arcs that comprise it and its opposite.
so
m ∠DEC=[Arc DC+Arc AB]/2------> [150+90]/2-----> 120°

the answer is
120°