A marble, a bead and a sticker costs $9.70 altogether.
The marble costs $1.10 less than the bead.
The sticker costs $2.40 more than the bead.
How much do 2 stickers cost?
Choose the cheapest item to be 1 u.
The marble costs $1.10 less than the bead.
The cheapest item is the marble.

Cost of the marble = 1 u
Cost of the bead = 1 u + 1.10
Cost of the sticker = 1 u + 1.10 + 2.40 = 1 u + 3.50

Total cost of the marble, the bead and the sticker
= 1 u + 1 u + 1.10 + 1 u + 3.50
= 1 u + 1 u + 1 u + 1.10 + 3.50
= 3 u + 4.6

3 u + 4.60 = 9.70
3 u = 9.70 - 4.60
3 u = 5.10

1 u = 5.10 ÷ 3 = 1.70

Cost of 2 stickers
= 2 x (1 u + 3.50)
= 2 x (1.70 + 3.50)
= 2 x 5.20
= $10.40

Answer(s): $10.40