((x-1)/4)=(2/5).
((x-1)/4)=(2/5)．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/4) + (2/5)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">(13/20) / (1/4)</gadget>
<output>13/5 = around 2.6</output>

<result>13/5 = around 2.6</result>