A barrel of oil weighs 150 kilograms. After (3/4) is used up, another 15 kilograms is poured out. At this time, the barrel of oil weighs 45 kilograms. How much does this oil barrel weigh?
一桶油连桶重150千克，用去(3/4)后，又倒出15千克，这时这桶油连桶重45千克，这只油桶重多少千克？
<gadget id="calculator">150 - 15 - 45</gadget>
<output>90</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">90 / (3/4)</gadget>
<output>120</output>

<gadget id="calculator">150 - 120</gadget>
<output>30</output>

<result>30</result>