Adam pays $22.70 for a marble, a bead and a sticker.
The marble costs $3.20 less than the bead.
The bead costs $1.60 less than the sticker.
What is the cost of 6 stickers more than 4 marbles?
Choose the cheapest item to be 1 u.

Cost of the marble = 1 u
Cost of the bead = 1 u + 3.20
Cost of the sticker = 1 u + 3.20 + 1.60 = 1 u + 4.80

Total cost of the marble, the bead and the sticker
= 1 u + 1 u + 3.20 + 1 u + 4.80
= 3 u + 8.00

3 u + 8.00 = 22.70
3 u = 22.70 - 8.00
3 u = 14.70

1 u = 14.70 ÷ 3 = 4.90

Cost of 6 stickers more than 4 marbles
= 6 x (1 u + 4.80) - 4 x 1 u
= 6 u + 28.80 - 4 u
= 2 u + 28.80
= 2 x 4.90 + 28.80
= 9.80 + 28.80
= $38.60

Answer(s): $38.60