Adam pays $25.50 for a marble, a bead and a sticker.
The marble costs $2.20 less than the bead.
The bead costs $1.30 less than the sticker.
What is the cost of 9 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 + 2.20
Cost of the sticker = 1 u + 2.20 + 1.30 = 1 u + 3.50

Total cost of the marble, the bead and the sticker
= 1 u + 1 u + 2.20 + 1 u + 3.50
= 3 u + 5.70

3 u + 5.70 = 25.50
3 u = 25.50 - 5.70
3 u = 19.80

1 u = 19.80 ÷ 3 = 6.60

Cost of 9 stickers more than 2 marbles
= 9 x (1 u + 3.50) - 2 x 1 u
= 9 u + 31.50 - 2 u
= 7 u + 31.50
= 7 x 6.60 + 31.50
= 46.20 + 31.50
= $77.70

Answer(s): $77.70