Which statement properly describes the formal charges on the atoms in SO4^2-?

Question

answer is 2 on sulfur and -1 on oxygen but I don't undrestand how?

please explain me ste pby step (4 is on the bottom and -2 is on top of SO)

Answer 1

Since this is a polyatomic ion, the sum of the formal charges add to poly's charge.

Oyxgen is "always" 2- .  You have 4 oxygens, for 8-.  What can you add to 8- to get 2-?  6+  Sulfur is 6+ in this ion.

Answer 2

Actually

Oyxgen is "always" 2- . You have 4 oxygens, for 8-. What can you add to 8- to get 2-? 6+ Sulfur is 6+ in this ion.