You have to optiosn to solve this. Let me explain both of them: The percent acidity, i.e. the percent acetic acid in a sample of vinegar is calculated by the following equation:
% acidity = (grams of acetic acid / grams of vinegar) x 100
The other method you can use is to remember that in order to calculate the percent acetic acid in the vinegar solution by mass you can assume the density of the vinegar solution is the same as water (1.00 g/ml). The formula will be:
grams of vinegar solution = density of vinegar solution x volume of vinegar solution
For example if 5 ml of the vinegar solution was used and if we assume that density of the vinegar solution is 1.00 g/ml then
grams of vinegar solution = 1.00 g / ml x 5 ml = 5 grams