In (3/(x))=(4/5), when x is equal to the number, the proportion can be formed.
(3/(x))=(4/5)中，当x等于多少时，才能组成比例．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">3 / (4/5)</gadget>
<output>15/4 = around 3.75</output>

<result>15/4 = around 3.75</result>