A worker wants to produce 300 machine parts. This worker produces 20 parts per hour. In this way, it has been produced for 8 hours. How many parts are left unproduced?
某工人要生产300个机器零件，这名工人每小时生产20个零件，照这样，已经生产了8小时，还剩下多少个零件没生产？
<gadget id="calculator">20 * 8</gadget>
<output>160</output>

<gadget id="calculator">300 - 160</gadget>
<output>140</output>

<result>140</result>