Here are two ways of making a total of $12$ from three different positive whole numbers:  $2 + 3 + 7 = 12$~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~$3 + 4 + 5 = 12$  How many ways are there of making a total of $15$ using three different positive whole numbers ? 
Overseas Competition->Knowledge Point->Counting Modules->Questions Involving Enumeration->Splitting Whole Numbers->Simple Splitting Numbers->Splitting Numbers (with required number of terms)