数学题:化肥厂计划用15天生产化肥4500吨，钱5天平均每天生产340吨，后又提高了产量，结果提前3天就完了工，后几天平均每天生产化肥多少吨？（用方程解）

数学题解答：设后几天每天生产x吨。

340×5 + (15-5-3)x = 4500

1700 + 7x = 4500

7x = 2800

x=400

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