If ҳ: (2/7) = (7/9): (1/3), then ҳ = how much.
如果ҳ：(2/7)=(7/9)：(1/3)，那么ҳ=多少．
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">7 / 9</gadget>
<output>7/9 = around 0.777778</output>

<gadget id="calculator">(2/7) * (7/9)</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(2/9) / (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>