rope is cut off (1/5), and then connected to 9 meters, the result is longer than the original (2/5), how many meters is the original length of this rope?
一条绳子截去(1/5)，后再接上9米，结果比原来还长(2/5)，这条绳子原来长多少米．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) - 1</gadget>
<output>-3/5 = around -0.6</output>

<gadget id="calculator">(1/5) + 1 + (-3/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">9 / (3/5)</gadget>
<output>15</output>

<result>15</result>