Guangming Township dug a canal. The original plan was to dig 320 meters per day, which could be completed in 15 days. Actually dig 80 meters more every day, how many days will the actual digging be completed? (answer with different knowledge)
光明乡挖一条水渠，原计划每天挖320米，15天可以挖完．实际每天多挖80米，实际多少天挖完？(用不同知识解答)
<gadget id="calculator">320 * 15</gadget>
<output>4_800</output>

<gadget id="calculator">320 + 80</gadget>
<output>400</output>

<gadget id="calculator">4_800 / 400</gadget>
<output>12</output>

<result>12</result>