What is the oxidation state of an individual phosphorus atom in po33−? express the oxidation state numerically (e. g., +1)?

First, consider the overall charge of the ion. This is -3.
We know that the overall charge is the sum of the charges of the constituent atoms. Moreover, oxygen exhibits a -2 charge usually. We will now use this information:

Sum of charges:

P + 3O = -3
P + 3(-2) = -3
P = +3

Therefore, phosphorus has a charge of +3 in the phosphate ion.