A． There are two barrels of oil in B, and barrel A weighs 15 kilograms. If 8 kilograms are poured into barrel B, then B is 4 times that of A. How many kilograms of oil does barrel B contain?
A．B两桶油，A桶油重15千克，如果倒8千克给B桶，则B就是A的4倍，B桶原来有油多少千克？
<gadget id="calculator">15 - 8</gadget>
<output>7</output>

<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<gadget id="calculator">28 - 8</gadget>
<output>20</output>

<result>20</result>