Titration Math

you titrate 5 ml of vinegar with NaOH. It takes 42.78mL of 0.1066NaOH. What is the concentration of the vinegar? 

Commercial products sometimes express concentration of a solute in solution as percent (m/V). That is percent of mass of solute per 100 mL of solution. The concentration of acetic acid in vinegar is 5%, so it should have 5g of acetic per 100mL of vinegar. What is experimental percentage of acetic acid in previous question? 

With the first half of the question, I thought I would use M1V1=M2V2, however I am not completely certain