A barrel of oil is used for the first time (1/4), and 5 kg more than the first time is used for the second time, leaving 7.5 kg in the barrel. How many kilograms of oil is in this barrel of oil?
一桶油，第一次用去(1/4)，第二次比第一次多用5千克，桶里还剩7.5千克．这桶油原来有油多少千克？
<gadget id="calculator">5 + 7.5</gadget>
<output>12.5</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4) - (1/4)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">12.5 / (1/2)</gadget>
<output>25</output>

<result>25</result>