The first generation of salt weighs (1/2) kg, if (3/5) of it is used, how many kg are left?
一代盐重(1/2)kg，用了它的(3/5)，还剩多少kg？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

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

<gadget id="calculator">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>