The formula to find how many different ways are there to choose a subgroup of r things from a group of n things is
[tex]\frac{n!}{(n-r)!}[/tex]Here, you have 7 trophies and you want to choose 4 of them, so you have
[tex]\frac{7!}{(7-4)!}\text{ = }\frac{5040}{6}=840[/tex]So there are 840 ways to choose your 4 trophies out of the 7 you have.
