Choose a three-digit number:

Ex: 234

Repeat this number in front of it:

234234

Now divide by 13:

234234 / 13 = 18018

Now divide the result by 11:

18018 / 11 = 1638

Divide the result again, only now by 7:

1638 / 7 = 234

The result is equal to the three digit number you had chosen: 234.