Needs to be updated. This is valid for the year 2005. Change the numbers in step 5 to 1758 and 1757.
Basically, you're multiplying your original number by 100, adding 2008 and then subtracting your birth year (your age). BTW, this does not work for anyone over 100.
Step 1: Call your number X.
Step 2: Multiply by 2 (2X).
Step 3: Add 5 (2X+5).
Step 4: Multiply by 50 ((2X+5)*50 yields (100X+250)).
Step 5: Add 1758 or 1757 ((100X+250+1758) yields (100X+2008), (100X+250+1757) yields (100X+2007)).
Step 6: Subtract the year you were born ((100X+2008-Y), (100X+2007-Y)) <- the 2008-Y is your age if you've had your birthday, 2007-Y is your age if you haven't had your birthday.
So, you're taking a convoluted path to say "take your original number, multiply by 100, and add your age."