Answer:
d= 70°
b= 40°
a=35°
c=35°
Explanation:
Before starting to answer the question it is important to understand that "vertical angles" are equal.
What are vertical angles?
b and 40° are vertical angles.
d and 70° are vertical angles.
So from that we can say,
d= 70°
b= 40°
The angle above "c" and angle above "a" are equal. It is shown in the figure. Lets take that angle as x. I have shown this in the attached figure.
Then,
c=x and a=x (vertical angles)
therefore, c=a.
So we can say a=c=x.
40°+d+x+c+b+70°+a+x=360° (Angles around a point is 360°)
40°+70°+a+a+40°+70°+a+a=360°
220°+4a=360°
4a=360°-220°
4a=140°
a=35°
but, a=c
therefore, c=35°