Vanessa's new business is thriving and she frequently has orders to post. She has run out of packing peanuts for the packages and is now wondering how many orders she has sent. Each large order needs 200g of packing peanuts while small orders need just 50g of packing peanuts. If Lisa has used a total of 800g of packing peanuts and she knows she has sent 3 large orders, how many small orders has Lisa sent?
Give me a detailed solution.