A marble, a bead and a sticker costs $8.30 altogether.
The marble costs $1.10 less than the bead.
The sticker costs $2.20 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 + 2.20 = 1 u + 3.30

Total cost of the marble, the bead and the sticker
= 1 u + 1 u + 1.10 + 1 u + 3.30
= 1 u + 1 u + 1 u + 1.10 + 3.30
= 3 u + 4.4

3 u + 4.40 = 8.30
3 u = 8.30 - 4.40
3 u = 3.90

1 u = 3.90 ÷ 3 = 1.30

Cost of 2 stickers
= 2 x (1 u + 3.30)
= 2 x (1.30 + 3.30)
= 2 x 4.60
= $9.20

Answer(s): $9.20