How much .25 molar NAOH would you need to add to 50 mL of 2.85 molar HCl to reach the equivalence point?
mols HCl = M x L = ?
mols NaOH = mols HCl (since there is 1 mol HCl reacting with 1 mol NaOH)
Then M NaOH = mols NaOH/L NaOH.
You know mols and M, solve for L NaOH.