The factory has 22.5 tons of coal and burned 6.3 tons in 7 days. According to this calculation, how many days can the remaining coal be burned?
工厂有煤22.5吨，7天烧了6.3吨，照这样计算，剩下的煤可以烧多少天？
<gadget id="calculator">22.5 - 6.3</gadget>
<output>16.2</output>

<gadget id="calculator">6.3 / 7</gadget>
<output>0.9</output>

<gadget id="calculator">16.2 / 0.9</gadget>
<output>18</output>

<result>18</result>