A simple and ELEGANT way of checking if one number is divisble by 11 is to sum the alternate digits of this number.
sum of digits starting with 7 = 7 + 9 + 2 + 2 = 20
Sum of digits starting with 8 = 8 + 5 + 7 = 20
Difference between these two sums = 0
Rule is that if this difference is divisible by 11, then the original number is divisible by 11.
Hence it is divisible by 11
