A sticker, a bead and a marble costs $7.60 altogether.
The sticker costs $1.30 less than the bead.
The marble costs $1.10 more than the bead.
How much do 5 marbles cost?
Choose the cheapest item to be 1 u.
The sticker costs $1.30 less than the bead.
The cheapest item is the sticker.

Cost of the sticker = 1 u
Cost of the bead = 1 u + 1.30
Cost of the marble = 1 u + 1.30 + 1.10 = 1 u + 2.40

Total cost of the sticker, the bead and the marble
= 1 u + 1 u + 1.30 + 1 u + 2.40
= 1 u + 1 u + 1 u + 1.30 + 2.40
= 3 u + 3.7

3 u + 3.70 = 7.60
3 u = 7.60 - 3.70
3 u = 3.90

1 u = 3.90 ÷ 3 = 1.30

Cost of 5 marbles
= 5 x (1 u + 2.40)
= 5 x (1.30 + 2.40)
= 5 x 3.70
= $18.50

Answer(s): $18.50