Please answer quickly, what is the measure of c

Explanation:

The only given number here is the 20 degree angle. So we'll start with that. This is an inscribed angle, which doubles to 2*20 = 40, and this is the measure of the arc the inscribed angle cuts off (inscribed angle theorem). Consequently, it means that central angle b is also 40 degrees.

With b = 40, we can see that c = 180-b = 180-40 = 140. This is because b+c = 180 as the two angles are supplementary.

hello,

as   long as they add up to 180 its correct.