You know that in case of burns with alkalis, the affected area of the skin is washed with water and then neutralized

You know that in case of burns with alkalis, the affected area of the skin is washed with water and then neutralized with a solution of acetic acid. Calculate the mass fraction in% of acetic acid in this solution, if 197 g of water and 3 g of acid were taken for its preparation

Let’s calculate the mass of the solution:
m (solution) = m (water) + m (acid) = 197 + 3 = 200 g.
Let’s calculate the mass fraction of acid in the solution: w = m (acetic acid) * 100 / m (solution) = 3 * 100/200 = 1.5%.