3 beads and 1 marble cost $18.70.
1 bead and 3 marbles cost $18.50.

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

(a)
3 beads + 1 marble = 18.70 --- (1)
1 bead + 3 marbles = 18.50 --- (2)

(1) + (2)
4 beads + 4 marbles = 18.70 + 18.50
4 beads + 4 marbles = 37.20 --- (3)

(3) _{÷ 4}
4 beads + 4 marbles = 37.20
1 bead + 1 marble = 37.20 ÷ 4
1 bead + 1 marble = 9.30 --- (4)

(b)
(2) - (4)
(1 bead + 3 marbles) - (1 bead + 1 marble) = 18.50 - 9.30
1 bead - 1 bead + 3 marbles - 1 marble = 9.20
2 marbles = 9.20
1 marble = 9.20 ÷ 2 = 4.60

Cost of 1 marble = $4.60

(c)
Substitute 1 marble = 4.60 into (4).
1 bead + 1 marble = 9.30
1 bead + 4.60 = 9.30
1 bead = 9.30 - 4.60 = 4.70

Cost of 1 bead = $4.70

(d)
(4) _{x 5}
1 bead + 1 marble = 9.30
5 x (1 bead + 1 marble) = 5 x 9.30
5 beads + 5 marbles = 46.50

Cost of 5 beads and 5 marbles = $46.50

Answer(s): (a) $9.30; (b) $4.60; (c) $4.70; (d) $46.50