Where can I find a web site or book where I can practice drawing DFAs from a language like  {w| w has at least three as and at least two bs} . It will be important to have access to the answer so as to check myself. I need the practice.
Where Can I Find DFA Practice?
finite automata
Well you have a little problem between your hands. The problem is that creating a DFA that generates some language $L$ have more than one solution. In fact if $L$ is regular then it have infinite solutions. If you are searching a book with answers it may not be usefull because your answer can be correct even though it is different from the one in the book.There is some methods to prove the correctness of a DFA using proof by induction but it is fairly difficult. If you are having problems generating DFA I wouldn't reccommend to try proving the correctness until you are more experienced into this topic.My teacher told me that the best you can do to be sure that your DFA is correct(when you skipping the proof of correctness) is do it in a sistematic way and understandable for anyone that reads it.