数宝：适用于少儿加减法计算的试卷
主要功能：1、自定义xxx以内加减法 2、改正错题 3、历史记录查看自己做过的题
Happy Maths: Test paper suitable for childrens addition and subtraction calculation
Main functions: 1. Customize addition and subtraction within xxx 2. Correct incorrect questions 3. View historical records of questions you have done