4 ways to wear all pants
5 ways to wear shirts
6 ways to wear ties
4*5*6=120 different combos
think of it like this
eample
2 pairs of pants and 3 pairs of shirts
a,b are the pants, and c,d,e are the shirts
the ways are below
ac
ad
ae
bc
bd
be
2*3=6, 6 ways
answer is 120 days