A piece of iron wire is 120 meters long, (1/4) is used for the first time, and (2/5) is used for the second time, how many meters are left?
一根铁丝长120米，第一次用去(1/4)，第二次用去(2/5)，还剩多少米？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/4) - (2/5)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">120 * (7/20)</gadget>
<output>42</output>

<result>42</result>