There is a barrel of oil, pour out the whole barrel (1/3) for the first time, pour out 15 kilograms for the second time, and there is still half a barrel of oil in the barrel at this time. How many kilograms of oil was in this barrel of oil?
有一桶油，第一次倒出全桶的(1/3)，第二次倒出15千克，此时桶里还剩半桶油．这桶油原来有多少千克油？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/2) - (1/3)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">15 / (1/6)</gadget>
<output>90</output>

<result>90</result>