A factory produces a batch of chemical fertilizers, and plans to produce 6.4 tons per day, which can be completed in 18 days. The actual extra production is 0.8 tons per day. How many days did it actually take to complete the task?
某厂生产一批化肥，计划每天生产6.4吨，18天可以完成．实际每天多生产0.8吨，实际用了多少天完成任务？
<gadget id="calculator">6.4 * 18</gadget>
<output>115.2</output>

<gadget id="calculator">6.4 + 0.8</gadget>
<output>7.2</output>

<gadget id="calculator">115.2 / 7.2</gadget>
<output>16</output>

<result>16</result>