Students will need to listen and then 'think backwards'. This set of worksheets may be handled two ways. Students need to listen carefully as the teacher reads each problem 2 or 3 times and write their answer on a paper or portable whiteboard, then hold it up for the teacher to see. Or, the worksheet may be given to individuals, or pairs, to discuss, analyze and compute each answer. This way it may be used as a center to which the students rotate. The answer key is included.