Question 900304
write as You Read along
n - (n/2 + 1/2)  = n/2 - 1/2  (left 9 1/2)
(n/2-1/2)/2 - 1/2 = (n/2 -2)/2 (left 3)
(n/2 - 2)/4 - 1/2 = 0 
solve:
(n/2 - 2)/4 = 1/2 
 n/2 - 2 = 8
 n/2 = 10
 n = 20