(3/20): (x-7) = 6.5: 13.
(3/20)：(x-7)=6.5：13．
<gadget id="calculator">3 / 20</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">6.5 / 13</gadget>
<output>0.5</output>

<gadget id="calculator">0.5 * 7</gadget>
<output>3.5</output>

<gadget id="calculator">(3/20) + 3.5</gadget>
<output>3.65</output>

<gadget id="calculator">3.65 / 0.5</gadget>
<output>7.3</output>

<result>7.3</result>