某次数学竞赛共有20道选择题,答对一题记5分,答错一题扣2分,不答记0分.某同学共得48分,那么他最多答对了几题?英语:A man from the UK remembered the correct order of 1820 playing cards,after seeing them just once.(用从句转换)
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设做对X道,错Y道5X-2Y=48 (1)X+Y≤20 (2)由(1)得,Y=(5X-48)/2 (3)把(3)带入(2)得7X≤88X≤88/7≈12.5所以,最多做对了12题._______________________A man from the UK remembered the correct order of 1820 playing ...