The entire Animals and Math eBook series covers the complete fundamental math skills for Preschool to 2nd Grade. Using the fun and creativity of art and the hands-on learning approach of Montessori philosophy, this series includes thought-provoking lessons using colorful pictures and hands-on exercises such as drawing and art. This H level book covers subtraction again, but this time with regrouping numbers. The problems in this book will involve breaking up tens, not just straightforward subtraction with digits. Students that have practiced addition and subtraction with single digit numbers beforehand should understand and excel. The abacus problems are retained as a helpful tool for subtraction.