there are 18 pieces of dark chocolate and the ratio of dark and white is 3:2 so we can divide 18 by 3.
18/3 = 6.
This means the ratio of dark chocolate to white as a 1:1 ratio would be 6:6 so we can multiply 6 by 2 to give us the total amount of pieces of white chocolate.
6*2 = 12.
Therefore there are 12 white chocolate pieces.