Rob2233 发表于 2017-2-23 21:45) v- _9 x3 z- Z A$ M
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, , V9 t) w8 e* g( C. F2 N这应该是比 ...
7 X {' O: R$ H$ _' Zthanks 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.