3 marbles and 1 bead cost $18.90.
1 marble and 3 beads cost $17.50.

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)
3 marbles + 1 bead = 18.90 --- (1)
1 marble + 3 beads = 17.50 --- (2)

(1) + (2)
4 marbles + 4 beads = 18.90 + 17.50
4 marbles + 4 beads = 36.40 --- (3)

(3) _{÷ 4}
4 marbles + 4 beads = 36.40
1 marble + 1 bead = 36.40 ÷ 4
1 marble + 1 bead = 9.10 --- (4)

(b)
(2) - (4)
(1 marble + 3 beads) - (1 marble + 1 marble) = 17.50 - 9.10
1 marble - 1 marble + 3 beads - 1 bead = 8.40
2 beads = 8.40
1 bead = 8.40 ÷ 2 = 4.20

Cost of 1 bead = $4.20

(c)
Substitute 1 bead = 4.20 into (4).
1 marble + 1 bead = 9.10
1 marble + 4.20 = 9.10
1 marble = 9.10 - 4.20 = 4.90

Cost of 1 marble = $4.90

(d)
(4) _{x 5}
1 marble + 1 bead = 9.10
5 x (1 marble + 1 marble) = 5 x 9.10
5 marbles + 5 beads = 45.50

Cost of 5 marbles and 5 beads = $45.50

Answer(s): (a) $9.10; (b) $4.20; (c) $4.90; (d) $45.50