(i think its easy idk lol) b) Anna, Brian and Cassidy go on a shopping trip. The number
of items that Anna buys is equal to the combined number of
items that Brian and Cassidy buys. The average item cost for
Anna was $5, Brian was $3, and Cassidy was $6, and the total
cost of the purchases was $120. If each item Anna bought was 4
oz, Brian was 3 oz, and Cassidy was 5 oz, the total ounces was
100 oz. How many items did each buy?

Define three variables and model the above with a system of
equations three equations. You do not have to solve the
system.