Question:
A shop sells 3 boxes of dark chocolates and 5 boxes of white chocolates for $26.60. This amount is before the 7% GST.
Zane had a card that gave him a 10% discount from the shop. He paid $67. 41 for 10 boxes of dark chocolates and 10 boxes of white chocolates. This amount is inclusive of the 7% GST.
(a) Find the usual price of a box of dark chocolates before the GST.
(b) During a sale, for every 3 boxes of dark chocolates purchased, one box of white chocolates was given free. Helen paid $105 for some boxes of dark chocolates. This amount is before the GST. How many boxes of white chocolates did she get for free?

Solution:
