3 is unique because whenever it is muptiplied by any number the answer adds up to a number that is divisible by 3.
such as 9x3 = 27 2+7 = 9
7x 3 = 21 2+1 =3
8x3 = 24 2+4 =6
3x 5 = 15 1+5 = 6
3x6 = 18 1=8 = 9,,,, never fails..
also numbers divisible by 3 same thing
9x8 + 72 /7+2 =9
9x9 = 81/ 8+1 = 9