Ответ:\(900:100=9\).\(81:9\cdot9\cdot1-1=9\cdot9-1=80\).\(81:81+64\cdot0=1+0=1\).\(510:3+58=170+58=228\).\(300:10=30\).\(28:(5-21:21)=28:(5-1)=7\).\(23\cdot10=230\).\(300:30=10\).\(400:4=100\).