A bundle of iron wire is 200m long, 30% of the total length is used for the first time, and 42% of the total length is used for the second time, how many meters are left?
一捆铁丝长200m，第一次用去全长的30%，第二次用去全长的42%，还剩多少米？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">42 / 100</gadget>
<output>21/50 = around 0.42</output>

<gadget id="calculator">1 - (3/10) - (21/50)</gadget>
<output>7/25 = around 0.28</output>

<gadget id="calculator">200 * (7/25)</gadget>
<output>56</output>

<result>56</result>