The canteen of Xiuli Middle School used 6.16 tons of coal this month, which was 12% less than last month. How many tons of coal was used last month?
秀丽中学的食堂本月用煤6.16吨，比上月节省了12%，上月用煤多少吨？
<gadget id="calculator">12 / 100</gadget>
<output>3/25 = around 0.12</output>

<gadget id="calculator">1 - (3/25)</gadget>
<output>22/25 = around 0.88</output>

<gadget id="calculator">6.16 / (22/25)</gadget>
<output>7</output>

<result>7</result>