問題詳情：
一次環保知識競賽共有25道題，規定答對一道題得4分，答錯或不答一道題扣1分.在這次競賽中，小明被評為優秀（85分或85分以上），小明至少答對了幾道題？
【回答】
解：設小明答對了x道題，·············································································· 6分
4x－(25－x) ≥85····························································································· 8分
x≥22····························································································· 9分
所以，小明至少答對了22道題.····································································· 10分
知識點：不等式
題型：解答題
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