Adam pays $26.40 for a marble, a bead and a sticker.
The marble costs $3.10 less than the bead.
The bead costs $1.30 less than the sticker.
What is the cost of 3 marbles less than 9 stickers?
Choose the cheapest item to be 1 u.

Cost of the marble = 1 u
Cost of the bead = 1 u + 3.10
Cost of the sticker = 1 u + 3.10 + 1.30 = 1 u + 4.40

Total cost of the marble, the bead and the sticker
= 1 u + 1 u + 3.10 + 1 u + 4.40
= 3 u + 7.50

3 u + 7.50 = 26.40
3 u = 26.40 - 7.50
3 u = 18.90

1 u = 18.90 ÷ 3 = 6.30

Cost of 3 marbles less than 9 stickers 
= 9 x (1 u + 4.40) - 3 x 1 u
= 9 u + 39.60 - 3 u
= 6 u + 39.60
= 6 x 6.30 + 39.60
= 37.80 + 39.60
= $77.40

Answer(s): $77.40