解；1/x-1/9x-20=1即9/9x-1/9x-20=1即8/9x=218/21=9xx=8/189
9/9x - 1/9x -20 = 18/9x - 20 =18/9x = 1 + 208/9x = 218 = 9x * 218 = 189xx = 8 / 189
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