The sum of the ages of Ding Ding, Dongdong and Dangdang is 31 years old, and Ding Ding is 12 years old this year, 3 years older than Dangdang. May I ask: How old is Dongdong this year?
丁丁、东东和当当三人的年龄和是31岁，丁丁今年12岁，比当当大3岁．请问：东东今年多少岁．
<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<gadget id="calculator">31 - 12 - 9</gadget>
<output>10</output>

<result>10</result>