5 marbles and 1 bead cost $26.90.
1 marble and 5 beads cost $19.30.

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 4 marbles and 4 beads.

(a)
5 marbles + 1 bead = 26.90 --- (1)
1 marble + 5 beads = 19.30 --- (2)

(1) + (2)
6 marbles + 6 beads = 26.90 + 19.30
6 marbles + 6 beads = 46.20 --- (3)

(3) _{÷ 6}
6 marbles + 6 beads = 46.20
1 marble + 1 bead = 46.20 ÷ 6
1 marble + 1 bead = 7.70 --- (4)

(b)
(2) - (4)
(1 marble + 5 beads) - (1 marble + 1 marble) = 19.30 - 7.70
1 marble - 1 marble + 5 beads - 1 bead = 11.60
4 beads = 11.60
1 bead = 11.60 ÷ 4 = 2.90

Cost of 1 bead = $2.90

(c)
Substitute 1 bead = 2.90 into (4).
1 marble + 1 bead = 7.70
1 marble + 2.90 = 7.70
1 marble = 7.70 - 2.90 = 4.80

Cost of 1 marble = $4.80

(d)
(4) _{x 4}
1 marble + 1 bead = 7.70
4 x (1 marble + 1 marble) = 4 x 7.70
4 marbles + 4 beads = 30.80

Cost of 4 marbles and 4 beads = $30.80

Answer(s): (a) $7.70; (b) $2.90; (c) $4.80; (d) $30.80