A pencil is originally 20 cm long, but 70 mm is used up, how many cm is left?
一枝铅笔原来长20厘米，用去了70毫米，还剩多少厘米？
<gadget id="calculator">70 / 10</gadget>
<output>7</output>

<gadget id="calculator">20 - 7</gadget>
<output>13</output>

<result>13</result>