The school bought a 200m long wire, used up the full length (2/5) for the first time, and used up 45% of the full length for the second time. How many meters of wire are left?
学校买来200m长的电线，第一次用去了全长的(2/5)，第二次用去全长的45%．还剩多少米电线？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (2/5) - (9/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">200 * (3/20)</gadget>
<output>30</output>

<result>30</result>