Complete the parts below. Write your answers as whole numbers or fractions in simplest form.

(a) One unit rate: 3 pieces of dark chocolate for each 1 piece of milk chocolate

Another unit rate: 6 pieces of dark chocolate for each 2 pieces of milk chocolate

(b) To find out how many pieces of milk chocolate are needed if 42 pieces of dark chocolate are used, we can set up a proportion using the given ratio:

36 dark chocolate / 12 milk chocolate = 42 dark chocolate / x milk chocolate

Cross multiplying, we get:

36x = 12 * 42

Simplifying,

36x = 504

Dividing both sides by 36,

x = 504 / 36

x = 14

Therefore, 14 pieces of milk chocolate are needed if 42 pieces of dark chocolate are used.