It is stipulated that * is a new operation symbol, and A*B=A*B+A, then (3*4)*5=how much.
规定*是一种新的运算符号，且A*B=A*B+A，那么(3*4)*5=多少．
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">12 + 3</gadget>
<output>15</output>

<gadget id="calculator">15 * 5</gadget>
<output>75</output>

<gadget id="calculator">75 + 15</gadget>
<output>90</output>

<result>90</result>