40-x+1/5=(1-1/5)x解：40又1/5-x=4/5x 9/5x=221/5 x=221/5÷9/5 x=221/9 x=24又5/9
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40-x+1/5x=(1-1/5)x解：40-4/5x=4/5x4/5x+4/5x=408/5x=40x=40÷8/5x=25
