Suppose "△" is a new calculation rule, 2△3=2+3+4=9, 5△4=5+6+7+8=26, ..., calculate according to this rule: 7△5=how much.
设"△"是一种新运算规则，2△3=2+3+4=9，5△4=5+6+7+8=26，…，按此规则计算：7△5=多少．
<gadget id="calculator">7 + 8 + 9 + 10 + 11</gadget>
<output>45</output>

<result>45</result>