Chapter 4 - Sections 4.1-4.9 - Exercises - Problems by Topic - Page 189: 92f

$H: +1$ , $S: +6$ , $O: -2$

O usually has an oxidation state of $-2$ and H usually has an oxidation state of $+1$. The sum of the oxidation states of a polyatomic ion is equal to its charge which in this case is $-1$. This means that the oxidation state of S is $+6$ as $(+1)+(+6)+4(-2)= -1$