is 5 years younger than B, and C is 10 years younger than the sum of the ages of A and B. If the sum of the ages of the three people is 80 years old, how old is B?
A比B小5岁，C比A和B岁数的总和小10岁．若三个人的岁数总和是80岁，B是多少岁．
<gadget id="calculator">5 + 15 + 80</gadget>
<output>100</output>

<gadget id="calculator">1 + 1 + 2</gadget>
<output>4</output>

<gadget id="calculator">100 / 4</gadget>
<output>25</output>

<result>25</result>