A bottle of oil, eat (1/2) for the first time, and eat the rest (1/5) for the second time. At this time, there are still 30 kilograms in the bottle. How many kilograms does this bottle of oil originally contain?
一瓶油，第一次吃去(1/2)，第二次吃去余下的(1/5)，这时瓶内还有30千克，这瓶油原来有多少千克？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">30 / (4/5) / (1/2)</gadget>
<output>75</output>

<result>75</result>