It is known that there is a mathematical symbol △ that makes the following equations true, 2△4=8, 5△3=13, 3△5=11, 9△7=25, then 7△3=how much.
已知有一个数学符号△使下列等式成立，2△4=8，5△3=13，3△5=11，9△7=25，那么7△3=多少．
<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">14 + 3</gadget>
<output>17</output>

<result>17</result>