Known: A#B=A*B/2, then 3#(5#7)=how much.
已知：A#B=A*B/2，那么3#(5#7)=多少．
<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">5 * (7/2)</gadget>
<output>35/2 = around 17.5</output>

<gadget id="calculator">(35/2) / 2</gadget>
<output>35/4 = around 8.75</output>

<gadget id="calculator">3 * (35/4)</gadget>
<output>105/4 = around 26.25</output>

<result>105/4 = around 26.25</result>