Because Dec 25 = Oct 31
Because oct 31 = dec 25
Because OCT 31 is the same as DEC 25.
Because DEC 25 = OCT 31
Because they're always trying to find the x. They don't know y, either.
L'Hospital.
Only once, and then you are subtracting it from 20.
Because it is only 2/5 solution.