There are two kinds of operations ◆ and ■: stipulate a b﹦a*ba, a b﹦a/b+a. Then (6◆5)■4﹦ how much.
有这样两种运算◆和■：规定a◆b﹦a*b-a，a■b﹦a/b+a．则(6◆5)■4﹦多少．
<gadget id="calculator">6 * 5</gadget>
<output>30</output>

<gadget id="calculator">30 - 6</gadget>
<output>24</output>

<gadget id="calculator">24 / 4</gadget>
<output>6</output>

<gadget id="calculator">6 + 24</gadget>
<output>30</output>

<result>30</result>