A sticker, a marble and a bead costs $9.50 altogether.
The sticker costs $3.50 less than the marble.
The bead costs $2.20 more than the marble.
How much do 3 beads cost?
Choose the cheapest item to be 1 u.
The sticker costs $3.50 less than the marble.
The cheapest item is the sticker.

Cost of the sticker = 1 u
Cost of the marble = 1 u + 3.50
Cost of the bead = 1 u + 3.50 + 2.20 = 1 u + 5.70

Total cost of the sticker, the marble and the bead
= 1 u + 1 u + 3.50 + 1 u + 5.70
= 1 u + 1 u + 1 u + 3.50 + 5.70
= 3 u + 9.2

3 u + 9.20 = 9.50
3 u = 9.50 - 9.20
3 u = 0.30

1 u = 0.30 ÷ 3 = 0.10

Cost of 3 beads
= 3 x (1 u + 5.70)
= 3 x (0.10 + 5.70)
= 3 x 5.80
= $17.40

Answer(s): $17.40