we know that
The measure of the interior angle is the half sum of the arcs comprising it and its opposite
so
m∠CED=

see the attached figure with letters to better understand the problem
° ------> by central angle
° ------> by central angle
Substitute the values in the formula above
m∠CED=

m∠CED=

m∠CED=
°
therefore
the answer is
m∠CED=
°