You are looking for the average. To find the average, one adds all terms and divides by the number of terms.
((1/2)+(5/6))/2
((3/6)+(5/6))/2
(8/6)/2
(4/6)
(2/3)
The answer is B) 2/3.
First you have to find a common denominator between all the fractions which would be 12 for the first week it would be reduced to 6 3/12 and the second 4 8/12 both added together would be 10 and 11/12 so the equation would be 15 4/12 - 10 11/12 which would be 4 5/12.
The formula for a circumference of a circle is 2πr
2 × π × 25 = 157
so your answer is A 157in.
I hope I've helped!