
David W. answered 08/28/15
Experienced Prof
There are some interesting ways to think about this problem (depending on the level of math that you use). For classes studying combinations and probabilities, there are formulas; for computer science classes, there are enumeration (list them all) techniques; for the beginning classes, there are pictures.
One of the most interesting ideas is that the number of cookies “counts” from 1 to 6 for each person (like a gas pump does, but the pump goes from 0 to 9 for units, then tens, then hundreds, then …). The “constraint” (limitation) is that the sum of the 3 digits must equal 8 (that’s why the counter goes from at least 1 to no more than 6). So, you could use a formula to determine how many or you could just list them all.