a 35.5 mL sample of an NaOH solution is needed to titrate a 2.08 g sample of pure benzoic acid (HC7H5O2)a solid. What is the molarity of the NaOH solution?

We'll call benzoic acid HB.

HB + NaOH ==> NaOH
mols HB = grms/molar mass
Look at the equation (the coefficients) 1 mol NaOH = 1 mol HB; therefore, mols HB = mols NaOH.
Then M NaOH = mols NaOH/L soln.