The ratio of the lengths of the two bundles of wire is 7:4. The first bundle takes 18m. The second bundle uses 6m, and the remaining wires are equal in length. How many meters was the first iron wire?
两捆铁丝的长度的比是7：4．第一捆用去18m．第二捆用去6m，剩下的铁丝长度相等．原来第一拥铁丝长多少米？
<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 - (4/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">12 / (3/7)</gadget>
<output>28</output>

<result>28</result>