The What to do when you can't... series of books builds on what you do know, to teach you what you do not know, and you will always know more than you think! What to do when you can't add and subtract uses effective learning methods, often involving multi-sensory ideas. Students are encouraged to use speaking, listening, writing and seeing to build knowledge of these core mathematical skills. The What to do when you can't... series of maths books are written for parents, teachers or students to use and contain clear explanations of how to build key skills. A fresh approach to core mathematical skills