A rope is 100 decimeters long, 3 meters are used for the first time, and 40 decimeters are used for the second time, how many decimeters are left?
一条绳子长100分米，第一次用了3米，第二次用了40分米，还剩多少分米？
<gadget id="calculator">3 * 10</gadget>
<output>30</output>

<gadget id="calculator">100 - 30 - 40</gadget>
<output>30</output>

<result>30</result>