Tom, Jerry, and Ruby all have cavities. They went to the dentist together. The doctor found that they had 8 cavities. How many cavities could each of them have?
汤姆、杰瑞和得鲁比都有蛀牙，他们一起去牙医诊所看病，医生发现他们一共有8颗蛀牙，他们三人可能分别有几颗蛀牙？
<gadget id="calculator">6 + 5 + 4 + 3 + 2 + 1</gadget>
<output>21</output>

<result>21</result>