First we find the measurement of dark dot .
ANd for that we have to use the formula of the angle formed by the intersection of chord .
Let the dark dot be t.
So we have

t and z are linear pair and sum of angles of linear pair =180 degree.
So we get

The answer for the following question is A) -b
Answer:
14x+4
Step-by-step explanation:
5x+5x+2x+2x+3+3-1-1
5x+5x+2x+2x=14x
3+3-1-1=4
14x+4