To answer this question, I would definitely use a diagram so that they can clearly see that this is a cycle and it will probably then use the diagram to explain each step. The Photosynthesis equation CO2 + Water + light = Glucose + O2The Calvin Cycle, or the light independent reaction (which means it can happen when it is light or when it is dark) is linked to the light dependent reaction. This is where is gets the first molecule of CO2.This CO2 molecule combines with a 5 carbon sugar called ribulose bisphosphate (can be simplified to RuBP). This makes a 6 carbon sugar and is catalysed by an enzyme called ribulose bisphosphate carboxylase (simplifies to Rubisco).This 6 carbon sugar breaks down into two 3 carbon sugars called glycerate-3-phosphate (GP). As the cycle continues, ATP and NADPH are reduced (loose electrons) in order to convert the 2 GP molecules into 2 molecules of triose phosphate (TP).After this, some of the TP molecules leave the cycle and become glucose (bear in mind the photosynthesis equation at this point) and the other molecules remain to regenerate RuBP and the cycle continues.