(12/13)-(2/91)=how much.
(12/13)-(2/91)=多少．
<gadget id="calculator">12 / 13</gadget>
<output>12/13 = around 0.923077</output>

<gadget id="calculator">2 / 91</gadget>
<output>2/91 = around 0.021978</output>

<gadget id="calculator">(12/13) - (2/91)</gadget>
<output>82/91 = around 0.901099</output>

<result>82/91 = around 0.901099</result>