Rob2233 发表于 2017-2-23 21:45: b9 r M! p3 Z! O; ?
如果觉得难度不够的话,可以试试加拿大公开赛(Canadian Open Mathematics Challenge)的题,* r9 @/ X* r' ?% h/ N
这应该是比 ...
, i: T+ F7 p3 t9 vthanks a lot as parents, but i guess my daughter going to hate you. i won't let her know who you are. please keep sending this kind good resource for all parents.