Answer:
3,003 different menus can be made showing 5 main courses from 15 choices
Explanation:
we need to find how many different menus can be made showing 5 main courses from 15 choices
Total of 15 choices
5 to be selected from 15 choice
'r' is selected from n choices in nCr ways

Here 5 is selected from 15 in 15C5 ways

So 3,003 different menus can be made showing 5 main courses from 15 choices