Ken has between 3 and 100 shells in his collection. If he counts his shells 3 at a time, he has 2 left over. If he counts them 4 at a time, he has 2 left over. If Ken counts them 5 at a time, he still has 2 left over. How many shells does Ken have in his shell collection?
(Source: Adapted from Mathematics Teaching in the Middle School, Mar-Apr 1996)