Oh! We should start with finding the lngths of the "curvy sides". As you can see there are 2 semi circles which we can combine to make one circle with a diameter of 7. The formula for the circumference of the circle is 2πr which is also equal to the diameter x π. SO the circumeference is 7π which is this case equals 22 since they are telling us to use π as 22/7. I'm not sure about the rest but I hope this helped a little!!
you can reason this concretely. suppose you start with 60 bugs. 1/5 of the 60 bugs is 12 bugs divide 12 bugs into 3 equal groups. each group has 12/3 = 4 bugs. the fraction now is 4/60 in lowest terms this is 1/15