A project, A needs 8 days to complete. If A has been repaired for 3 days, there are still 50 meters left. How many meters has A been repaired?
一项工程，甲需要8天才能修完．如果甲修了3天，还剩下50米．甲已经修了多少米？
<gadget id="calculator">8 - 3</gadget>
<output>5</output>

<gadget id="calculator">50 / 5</gadget>
<output>10</output>

<gadget id="calculator">10 * 3</gadget>
<output>30</output>

<result>30</result>