Math Help - seemingly simple, but very complicated to solve combination

1. seemingly simple, but very complicated to solve combination

Consider a man who wishes to purchase 12 donuts. There are 6 kinds of donuts. How many different combinations of donuts can he purchase?

2. To select k items from n different varieties, there are ${{k+n-1} \choose k}$ ways to do that.

3. wow thanks
i have never heard of that formula but it certainly works

4. Originally Posted by cubs3205
wow thanks
i have never heard of that formula but it certainly works
Here is the way it works.