There are 15 tons of steel in the warehouse, and (1/5) of the total is used for the first time, and 50% of the total is used for the second time. How many tons of steel are left?
仓库里有15吨钢材，第一次用去总数的(1/5)，第二次用去总数的50%，还剩下多少吨钢材？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/5) - (1/2)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">15 * (3/10)</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>