There are some three-digit numbers in which none of the digits is 0, and the sum of the digits is 6. How many such three-digit numbers are there?
有一些三位数的各位数字都不是0，且各位数字之和为6，这样的三位数共有多少个？
<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">3 + 6 + 1</gadget>
<output>10</output>

<result>10</result>