A pile of (7/8) tons of coal, (1/5) tons is removed for the first time, how many tons are left.
一堆煤(7/8)吨，第一次运走(1/5)吨，还剩下多少吨．
<gadget id="calculator">7 / 8</gadget>
<output>7/8 = around 0.875</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(7/8) - (1/5)</gadget>
<output>27/40 = around 0.675</output>

<result>27/40 = around 0.675</result>