new calculation is now stipulated: a*b=((a+b)/2), then 7*9=how much.
现规定一种新的运算：a*b=((a+b)/2)，则7*9=多少．
<gadget id="calculator">7 + 9</gadget>
<output>16</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<result>8</result>