Use a bundle of ropes 150 meters long to surround a rectangular nursery with a length of 40 meters and a width of 30 meters. How many meters are left?
用一捆长150米的绳子，将一个长40米，宽30米的长方形苗圃围一周，还剩多少米？
<gadget id="calculator">40 + 30</gadget>
<output>70</output>

<gadget id="calculator">70 * 2</gadget>
<output>140</output>

<gadget id="calculator">150 - 140</gadget>
<output>10</output>

<result>10</result>