For a colored ribbon, cut off the full length (3/8) for the first time, and cut off 15 meters for the second time. How much rice?
一根彩带，第一次剪去全长的(3/8)，第二次剪去15米，这时剪去的与剩下的米数之比为7：5，第一次剪去了多少米？
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">(7/12) - (3/8)</gadget>
<output>5/24 = around 0.208333</output>

<gadget id="calculator">15 / (5/24)</gadget>
<output>72</output>

<gadget id="calculator">72 * (3/8)</gadget>
<output>27</output>

<result>27</result>