Use a rope to measure the length of the table, fold it in half once and measure the rope is 0.7 meters longer than the table, and fold it in half three times to measure the rope is 0.2 meters shorter than the table. How long is the rope? (solution by equation)
用一根绳子测量桌子的长度，对折一次量绳子比桌子还长0.7米，对折三次的量绳子比桌子短0.2米．请问绳子有多长？(用方程解)
<gadget id="calculator">0.7 + 0.2</gadget>
<output>0.9</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/2) - (1/8)</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">0.9 / (3/8)</gadget>
<output>2.4</output>

<result>2.4</result>