A pile of apples weighs (7/9) tons, and (2/9) tons are removed, how many tons are left?
一堆苹果重(7/9)吨，运走了(2/9)吨，还剩多少吨？
<gadget id="calculator">7 / 9</gadget>
<output>7/9 = around 0.777778</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">(7/9) - (2/9)</gadget>
<output>5/9 = around 0.555556</output>

<result>5/9 = around 0.555556</result>