The original batch of steel in the building material warehouse, 20% of the original steel was shipped out for the first time, and (3/5) of the original steel was shipped out for the second time. At this time, there were still 15 tons of steel in the warehouse. How many tons?
建材仓库原有一批钢材，第一次运出原有钢材的20%，第二次又运出原有钢材的(3/5)，这时仓库中还剩下15吨钢材，这批钢材原有多少吨？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (1/5) - (3/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15 / (1/5)</gadget>
<output>75</output>

<result>75</result>