There are three barrels of oil. Pour 20 grams from barrel A to barrel B, then pour 35 grams from barrel B to barrel C, and finally pour 25 grams from barrel C to barrel A. At this time, the oil in the three barrels is exactly 100 grams. How many grams of oil is in barrel A?
有三桶油．从甲桶中倒20克到乙桶，然后从乙桶中倒35克到丙桶，最后从丙桶中倒25克到甲桶，这时三桶油都正好100克．原来甲桶中有油多少克．
<gadget id="calculator">20 - 25</gadget>
<output>-5</output>

<gadget id="calculator">100 + (-5)</gadget>
<output>95</output>

<result>95</result>