book has 270 pages. Xiaohua has already read (4/9) of this book. How many pages are left?
一本书270页，小华已经看了这本书的(4/9)，还剩多少页没看？
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">270 * (4/9)</gadget>
<output>120</output>

<gadget id="calculator">270 - 120</gadget>
<output>150</output>

<result>150</result>