My brother began to do oral calculations on demand with Rong's exercise book from the first volume of senior one. At first, my brother didn't count quickly. He does Rong's oral arithmetic problems every day, and his cards make rapid progress. By the time of the final exam, the whole team will have a little oral calculation questions, and all kinds of on-demand questions are very rich and detailed. I use Rong's book to explain my medium height. My brother got 98 points in the final exam, and I am very special.