To build a canal, the full length (3/8) was repaired for the first time, and 15 meters was repaired for the second time. At this time, the ratio of the repaired to the remaining is 7:5. How many meters did you repair for the first time?
修一条水渠，第一次修了全长的(3/8)，第二次修15米，这时已修的与剩下的比为7：5．第一次修了多少米？
<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">1 - (3/8) - (5/12)</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>