You will need a calculator.
First, pick a phone number.. (home, work, friend, or any number)
Enter the first 3 nubmers. (734-XXXX)
Multiply it by 80.
Add 1.
Multiply it by 250.
Now add last 4 numbers. (XXX-2782)
Add last 4 numbers again.
Subtract 250.
Finally, divide it by 2.
What numbers do you see?