The school cafeteria brings (2/5) tons of coal and uses up (1/4), how many tons are left?
学校食堂运来(2/5)吨煤，用去它的(1/4)，还剩下多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(2/5) * (3/4)</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>