已知:(□+△)×0.3=4.2 □÷0.4=12
求:□=____
△=____
Studying in groups is necessary __________ you want to do well in school.
隋朝一位余杭书生,到洛阳参加科举考试,如果走运河水路,下列哪段运河他不必经过( )