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So by divisibility rule of 11 we know that
 we have to add all even digits and from there we have to substract the sum of all odd digits if the result is 0 or a mltiple of 11 then the number is divisible by 11 or not
so here 
9 - 20 = -11 
so -11 is a multiple of 11 so the number is divisible by 11.