A barrel of oil uses 7 kilograms, and the remaining 25% is used. How many kilograms are left?
一桶油用去了7千克，用去的是剩下的25%，剩下的是多少千克？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">7 / (1/4)</gadget>
<output>28</output>

<result>28</result>