Permutation Puzzle

You are eating lunch on a table and there are ten flies on the table. With a quick swat you are able to kill three flies. How many flies are left on the table?

I have 20 books and I label them with their number. I take eight out to read. How many books are left?

This number added to it’s square, and the digits of that summation added together, bring it back to itself. What is the number?

A simple peasant bought a number of camels and is taking them to his farm. As he rides contentedly along he counts them – he counts 29. He was sure he had bought 30 camel, so in alarm he jumps off his camel and counts the camels again. To his delight there are 30. Half an hour later, he counts his camels and once more there are just 29. Confused, he climbs off his camel and counts again. Once more there are 30. Can you explain?

Fill in the blanks to complete the sequence:
……… + 13 * ……… / ……… + ……… + 12 *……… – ……… – 11 + ……… * ……… / ……… – 10 = 66

(Note: fill in the above blank with the digits 1 to 9, using each digit only once.)