To determine the age (or the number picked),
take the units digit of the answer and add it to the rest of the number.

1. Think of your age (or any number greater than 9).	Let's think of 136.
2. Multiply by 10.	Then we get 1360.
3. Now pick a number less than or equal to 9.	Let's pick 3.
4. Multiply it by 9.	Now we get 27.
5. Subtract the two results (step 2 and step 4).	We get 1360 - 27 = 1333.
6. Ask for the answer.	We are told 1333, so add the units digit (3) to the rest of the number (133)   to obtain 136 (the original number).