A pile of coal weighs 15 tons, and 3 tons are used up, what fraction of the total amount is left?
一堆煤重15吨，用去了3吨，还剩下总数的几分之几？
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">12 / 15</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>