0.64 M and 3.8% (lower than claim) First, you want to start by using the titration information to find the molarity of the acetic acid. M_1*V_1=M_2*V_2 Where 1 is the acetic acid and 2 is the sodium hydroxide. The product of molarity and volume of the sodium hydroxide provides the moles of the solution and the moles are equal in the acetic acid when completely titrated. M_1*V_1="moles"_2 ... More @Wikipedia
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