If Adam buys 5 beads and 6 marbles, it costs $85.70.
If Adam buys 6 beads and 5 marbles, he will have $4.20 left.

1. Find the cost of 1 bead and 1 marble.
2. Find the cost of 1 bead.
3. Find the cost of 1 marble.

(a)
5 beads + 6 marbles = 85.70 --- (1)
6 beads + 5 marbles = 85.70 - 4.20 = 81.50 --- (2)

(1) + (2)
11 beads + 11 marbles = 167.20 --- (3)

(3) _{÷ 11}
1 bead + 1 marble = 167.20 ÷ 11 = 15.20 --- (4)

Cost of 1 bead and 1 marble = $15.20

(b)
(4) _{x 5}
5 beads + 5 marbles = 5 x 15.20 = 760 --- (5)

(2) - (5)
6 beads + 5 marbles - 5 beads - 5 marbles = 81.50 - 760
6 beads - 5 beads - 5 marbles + 5 marbles = 5.50
1 bead = 5.50

Cost of 1 bead = $5.50

(c)
Substitute 1 bead = 5.50 into (4).

1 bead + 1 marble = 15.20
5.50 + 1 marble = 15.20
1 marble = 15.20 - 5.50 = 9.70

Cost of 1 marble = $9.70

Answer(s): (a) $15.20; (b) $5.50; (c) $9.70