Regulations: a⊗b=((2*a*b)/(a+b)), then 2⊗3=how much.
规定：a⊗b=((2*a*b)/(a+b))，那么2⊗3=多少．
<gadget id="calculator">2 * 2 * 3</gadget>
<output>12</output>

<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">12 / 5</gadget>
<output>12/5 = around 2.4</output>

<result>12/5 = around 2.4</result>