20% of a wire is used up, and 30 meters are connected, and it is now longer than the original (1/10), how many meters is the original wire?
一根电线用去20%，又接上30米，这时比原来长(1/10)，原来这根电线长多少米？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) - 1</gadget>
<output>-9/10 = around -0.9</output>

<gadget id="calculator">(1/5) + 1 + (-9/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">30 / (3/10)</gadget>
<output>100</output>

<result>100</result>