The cafeteria brought in a batch of coal. It was planned to burn 90 kilograms per day and burn it out in 8 days. The actual saving was 10 kilograms per day. How many days did it actually burn?
食堂运进一批煤，计划每天烧90千克，8天烧完，实际每天节约10千克，实际烧了多少天？
<gadget id="calculator">90 - 10</gadget>
<output>80</output>

<gadget id="calculator">8 / 80</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">90 * (1/10)</gadget>
<output>9</output>

<result>9</result>