Imagine a Story ...
	“In Kim’s chem class the professor assigned challenge problems worth extra credit, but each week Kim couldn’t do them and asked for help. The teacher said, ‘Don’t give up, attempt the problem again each day.’ Kim followed the advice and was eventually able to solve the problems.” Abstracting from the situation: A good problem-solving technique is to return later to a problem. • Some aspects are relevant • Some aspects are irrelevant