2 marbles and 1 bead cost $12.80.
1 marble and 2 beads cost $11.50.

1. Find the cost of 1 marble and 1 bead.
2. Find the cost of 1 bead.
3. Find the cost of 1 marble.
4. Find the cost of 5 marbles and 5 beads.

(a)
2 marbles + 1 bead = 12.80 --- (1)
1 marble + 2 beads = 11.50 --- (2)

(1) + (2)
3 marbles + 3 beads = 12.80 + 11.50
3 marbles + 3 beads = 24.30 --- (3)

(3) _{÷ 3}
3 marbles + 3 beads = 24.30
1 marble + 1 bead = 24.30 ÷ 3 
1 marble + 1 bead = 8.10 --- (4)

Cost of 1 marble and 1 bead = $8.10

(b)
(2) - (4)
(1 marble + 2 beads) - (1 marble + 1 marble) = 11.50 - 8.10
1 marble - 1 marble + 2 beads - 1 bead = 3.40
1 bead = 3.40

Cost of 1 bead = $3.40

(c)
Substitute 1 bead = 3.40 into (4).
1 marble + 1 bead = 8.10
1 marble + 3.40 = 8.10
1 marble = 8.10 - 3.40 = 4.70

Cost of 1 marble = $4.70

(d)
(4) _{x 5}
1 marble + 1 bead = 8.10
5 x (1 marble + 1 marble) = 5 x 8.10
5 marbles + 5 beads = 40.50

Cost of 5 marbles and 5 beads = $40.50

Answer(s): (a) $8.10; (b) $3.40; (c) $4.70; (d) $40.50