For a bundle of wires, half of the total length is used for the first time, more than 3 meters, the remaining half is used for the second time, less than 10 meters, 15 meters are used for the third time, and 7 meters are left in the end. How many meters is this bundle of wires originally?
一捆电线，第一次用去全长的一半多3米，第二次用去余下的一半少10米，第三次用去15米，最后还剩7米．这捆电线原来有多少米？
<gadget id="calculator">7 - 10</gadget>
<output>-3</output>

<gadget id="calculator">15 + (-3)</gadget>
<output>12</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">24 + 3</gadget>
<output>27</output>

<gadget id="calculator">27 * 2</gadget>
<output>54</output>

<result>54</result>