It is likely that you will be asked questions on material you have not yet learned. On such questions it is appropriate to answer, "I don't know." On any question that you have familiarity with, however, it is important to do your best. "I don't know" is interpreted by ALEKS to mean that you do not know the topic, and this will be reflected in the assessment results. Try your best to solve any problems that you think you might be able to solve. It is better to answer incorrectly on a topic that you have seen before, than to use the "I don't know" button and then skip related topics.