It is stipulated that x△y=Axy, x▽y(x+y)/2, and (1△3)▽3=1△(3▽3), then (1△3)▽3=how much.
规定x△y=Axy、x▽y(x+y)/2，且(1△3)▽3=1△(3▽3)，则(1△3)▽3=多少．
<gadget id="calculator">1.5 * 1 * 3</gadget>
<output>4.5</output>

<gadget id="calculator">4.5 + 3</gadget>
<output>7.5</output>

<gadget id="calculator">7.5 / 2</gadget>
<output>3.75</output>

<result>3.75</result>