Answer:
B 50˚
Explanation:
What you want to do is to find all other measures and subtract them from 360, or find all measures to the left of BE, and subtract from 180.
You can find mCE easily: since the measure of an arc is twice the measure of its corresponding angle (as long as that angle is not a central angle), mCE = 2(25), or 50˚.
mDE equals 100˚. This is because it and arc BD are the only arcs right of BE, the diameter, meaning they, together, must equal half the circle. Since half a circle = 180˚,
180˚=80˚+x
x=180-80
x=100
Now, you can solve:
Method 1:
360˚=80˚+80˚+50˚+100˚+x
360-80-80-50-100=x
x=50˚
Method 2:
180˚=80˚+50˚+x
x=180-80-50
x=50˚
This corresponds to answer choice B.