Given x※y=(x+y)/2, find (12※5)※3.
已知x※y=(x+y)/2，求(12※5)※3．
<gadget id="calculator">3.5 + 3</gadget>
<output>6.5</output>

<gadget id="calculator">6.5 / 2</gadget>
<output>3.25</output>

<result>3.25</result>