Collecting Baseball Cards
Mike collects baseball cards. Every day after the first day he gets 10 new cards. Every third day, he gives 3 cards to his sister. If Mike has 9 cards on the first day, on what day will he have exactly 100 cards?

Extensions 
Suppose Mike gave w cards to his sister every 3 days. In terms of w, on what day will he have exactly 100 cards?
(Source: Adapted from Mathematics Teaching in the Middle School, MarApr 1996) 
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