thats weird but guys i think i figured it out..
u can only use 2 digits right?
we'l take 11 for instance. u add them 1+1=2. and u substract it from the first no. 11-2=9..
just like that suppose we take 15. 1+5=6. then 15-6=9..
so 9 comes inevery instance when u take the first number of the...