You can put this solution on YOUR website! This is an interesting questions because of the wording.
4*7*3 =84 different outfits.
But the question asks not not many arrangements but how many he can wear.
Wear at one time?
Wear one after the other?
or how many outfits can he choose from the first time before any are dirty?
Let's say he wore one pair of pants, one shirt and a pair of shoes.
Can he wear them again? or does he need to wash them?
We haven't even got into his diet and clothes size
Maybe only half of them fit him.