Calculating the pH of a sodium phosphate solution [closed]

I have the following question in a chemistry homework:

Calculate the $$\mathrm{pH}$$ of a solution made by dissolving $$\pu{113 g}$$ of sodium phosphate in enough water to make a solution with a final volume of $$\pu{475 mL}$$. Find the equilibrium concentration of all species present in this solution.

It shouldn't be that hard of a problem, but my teacher really doesn't explain well at a distance (with the COVID-19 situation). I have found that it dissociates into $$\ce{NaOH}$$ and $$\ce{H3PO4}$$ when in water: $$\ce{Na3PO4(s) + 3H2O(l) → 3NaOH(aq) + H3PO4(aq)}$$

But I don't really know what to do next...

• No of course not, but if $Na_3PO_4$ dissociates and just the $PO_4$ ion reacts with water, it could make $HPO_4$, $H_2PO_4$ or $H_3PO_4$, right? – Thibaut B. Apr 30 '20 at 15:50
• Yes, right, but you need to quantify that. Technote: If you use mhchem MathJax extension, you can Write formulas as \$\ce{H3PO4}\$ what will look like $\ce{H3PO4}$ – Poutnik Apr 30 '20 at 15:52