For a rope, cut off the full length (3/8) for the first time, and cut off 7.5 meters for the second time. At this time, the ratio of the number of meters cut to the remaining meters is 7:5. How many meters are cut off for the first time? ?
一根绳子，第一次剪去全长的(3/8)，第二次剪去7.5米，这时剪去的与剩下的米数比是7：5，第一次剪去多少米？
<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">7.5 / (5/24)</gadget>
<output>36</output>

<gadget id="calculator">36 * (3/8)</gadget>
<output>27/2 = around 13.5</output>

<result>27/2 = around 13.5</result>