10 minutes before the lesson ends, teacher ask student representatives to work out the solutions on the blackboard so that everyone in the class can have a check and reference. The student representatives may be chosen from groups assigned by teacher or students just organize by themselves. Students are also instructed to check and mark their own solutions against those written on the blackboard, which may or may not be correct at all. The teacher can then review, comment, ask, consolidate the solutions on the blackboard to the whole class. (10 mins)