rope, cut off (5/7) for the first time, and cut off the remaining (1/6) for the second time, leaving 30 meters. How many meters is this rope originally? (solution by equation)
一根绳子，第一次剪去(5/7)，第二次剪去余下的(1/6)，还剩30米．这根绳子原来有多少米？(用方程解)
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(5/7) * (1/6)</gadget>
<output>5/42 = around 0.119048</output>

<gadget id="calculator">1 - (5/7) - (1/6)</gadget>
<output>5/42 = around 0.119048</output>

<gadget id="calculator">(5/42) + (5/42)</gadget>
<output>5/21 = around 0.238095</output>

<gadget id="calculator">30 / (5/21)</gadget>
<output>126</output>

<result>126</result>