There are natural numbers a, b. The definition is as follows: a*b=(a+b)/2, find the value of 3*(6*8).
有自然数a，b．定义如下：a*b=(a+b)/2，求3*(6*8)的值．
<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<result>5</result>