Here is the answer to the problem above. Given that a necktie is sold per dozen and costs $30.00 and sells it for $5. In order for us to know the price per necktie, we just have to divide 30 by 12 since one dozen is 12. 30 divided by 12, and the answer is 2.5. So the cost of one tie is $2.5. Hope this answers your question.