There is a mathematical operation symbol "⊙", which makes the following formulas true: 2⊙4=8, 4⊙6=14, 5⊙3=13, 8⊙7=23. According to this rule, 9⊙3=how much.
有一个数学运算符号"⊙"，使下列算式成立：2⊙4=8，4⊙6=14，5⊙3=13，8⊙7=23．按此规定，9⊙3=多少．
<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">18 + 3</gadget>
<output>21</output>

<result>21</result>