A29.00 ml sample of an unknown h3po4 solution is titrated with a 0.130 m naoh solution. the equivalence point is reached when 27.73 ml of naoh solution is added.

I am first assuming that you want the molarity of the acid. Use the formula  which is the titration formula. M is molarity (a is of acid and b is of base) and V is volume in mL (a is of acid and b is of base).  Plugging in gives us . Solving gives us 

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