Sentence:  I mean if you go in and want to <WSD>challenge</WSD> an exam it cost you half of your course money. If you don't pass the exam, that money is credited toward taking the course. What have you got to lose to <WSD>challenge</WSD> an exam, or do a competency exam? 
Meaning of the word marked with <WSD> tags:  To take (a final exam) in order to get credit for a course without taking it.