There is a pile of coal in a factory, (2/3) tons are used up, and (4/5) tons are left. How many tons is this pile of coal?
某工厂有一堆煤，用去(2/3)吨，还剩(4/5)吨．这堆煤有多少吨？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">(2/3) + (4/5)</gadget>
<output>22/15 = around 1.466667</output>

<result>22/15 = around 1.466667</result>