20% of a batch of steel is used for the first time, and (1/2) ton is used for the second time, leaving 3 tons. How many tons are there in this batch of steel?
一批钢材第一次用去20%，第二次用去(1/2)吨，还剩下3吨，这批钢材有多少吨？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 + (1/2)</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">20 / 100</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">(7/2) / (4/5)</gadget>
<output>35/8 = around 4.375</output>

<result>35/8 = around 4.375</result>