Squigly Squigly's Brain Teasers

Question:

What has 4 legs at the beginning of its life, 2 in the middle and 3 at the almost end of its life?

Answer:

A human: crawling, walking, using a cane.

Try another Brain Teaser:

If 7 is transformed into 13 and 11 is changed to 21 then what does 16 become?