John always wears a shirt, pants, socks, and shoes. he owns 121212 pairs of socks, 333 pairs of shoes, 555 pairs of pants, and 555 shirts.

If you mean the quantity of ways to dress John, 
he can choose any one of his 12 pairs of socks to combine with any one of his 3 pairs of shoes and any one of his 5 pairs of pants and any one of his 5 shirts.
12 ways to choose pair of socks and 3 ways to choose pair of shoes and 5 ways to choose pant and also 5 ways to choose a shirt.
12*3*5*5=900.
900 ways to dress him...