Adam pays $29.70 for a marble, a bead and a sticker.
The marble costs $3.70 less than the bead.
The bead costs $1.60 less than the sticker.
What is the cost of 3 stickers more than 2 marbles?
Choose the cheapest item to be 1 u.

Cost of the marble = 1 u
Cost of the bead = 1 u + 3.70
Cost of the sticker = 1 u + 3.70 + 1.60 = 1 u + 5.30

Total cost of the marble, the bead and the sticker
= 1 u + 1 u + 3.70 + 1 u + 5.30
= 3 u + 9.00

3 u + 9.00 = 29.70
3 u = 29.70 - 9.00
3 u = 20.70

1 u = 20.70 ÷ 3 = 6.90

Cost of 3 stickers more than 2 marbles
= 3 x (1 u + 5.30) - 2 x 1 u
= 3 u + 15.90 - 2 u
= 1 u + 15.90
= 1 x 6.90 + 15.90
= 6.90 + 15.90
= $22.80

Answer(s): $22.80