There are two barrels of oil, A and B. If 15 catties of oil is poured from barrel A into barrel B, the weight of the two barrels will be equal; How much is the original oil in barrel A?
有甲、乙两桶油，若从甲桶倒入乙桶15斤，则两桶油重量相等；若从乙桶倒入甲桶48斤，则甲桶油是乙桶油重量的4倍．甲桶原有油多少斤．
<gadget id="calculator">4 * 48</gadget>
<output>192</output>

<gadget id="calculator">192 + 30 + 48</gadget>
<output>270</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">270 / 3</gadget>
<output>90</output>

<gadget id="calculator">90 + 30</gadget>
<output>120</output>

<result>120</result>