The factory planned to process a batch of parts in 8 days, but actually processed 3 more parts per day than planned, so the task was completed in only 7 days. How many parts are there in this batch? (column equation solution)
工厂计划用8天时间加工一批零件，实际由于每天比计划多加工了3个，结果只用了7天就完成了任务．这批零件有多少个？(列方程解答)
<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<gadget id="calculator">8 - 7</gadget>
<output>1</output>

<gadget id="calculator">21 / 1</gadget>
<output>21</output>

<gadget id="calculator">21 * 8</gadget>
<output>168</output>

<result>168</result>