When you say two angles are complementary, they add up to 90 degrees.
Since two angles are the ratio 2:7, you can represent the smaller angle as 2x and the larger as 7x.
add them up as 2x+7x=90
the angles are 2x=20 degrees and 7x=70 degrees
so the smaller angle is 20 degrees
a = 3.14
b = 18
c = 18/5 or 3.6 or 3 3/5
not sure but it may be b, as i said i'm not sure.