i) there are 360 degrees in a circle. So subtract all the numbers from 360 to get the angle for econ.
That angle is 65 degrees
ii) If 95 degrees represents 228 books, then 360 degrees represents "x" (total) books. So we have an equation:
95 = 360
228 x
Solve for x, and we get x = 864
iii) The percentage is 80 degrees out of 360 degrees or 2/9 or roughly 0.222 or 22.2%