The answer to this riddle/joke is "hardened criminal".
You can also benefit from solving this riddle/joke by finding the answers to this math exercise with binomials and radicals.
Want more jokes? See how far you can go with a straight face with Short-Funny.com's top 100 funny jokes.
Of interest, check out the 10 best internet puzzles, optical illusions and brainteasers to exercise your mind, featured at IBMTimes.co.uk.