(3+4+5+6+...+14+15)/13.
(3+4+5+6+…+14+15)/13．
<gadget id="calculator">3 + 15</gadget>
<output>18</output>

<gadget id="calculator">13 / 2</gadget>
<output>13/2 = around 6.5</output>

<gadget id="calculator">18 * (13/2)</gadget>
<output>117</output>

<gadget id="calculator">117 / 13</gadget>
<output>9</output>

<result>9</result>