There are 15 tons of cement in the warehouse. Use 20% of the total on the first day, and use (1/2) tons on the second day. How many tons of cement are left in the warehouse?
仓库里有15吨水泥．第一天用去总数的20%，第二天用去(1/2)吨．仓库里还剩下水泥多少吨？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15 * (1/5)</gadget>
<output>3</output>

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

<gadget id="calculator">15 - 3 - (1/2)</gadget>
<output>23/2 = around 11.5</output>

<result>23/2 = around 11.5</result>