If Adam buys 3 marbles and 4 beads, it costs $47.90.
If Adam buys 4 marbles and 3 beads, he will need another $3.60.

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

(a)
3 marbles + 4 beads = 47.90 --- (1)
4 marbles + 3 beads = 47.90 + 3.60 = 51.50 --- (2)

(1) + (2)
7 marbles + 7 beads = 99.40 --- (3)

(3) _{÷ 7}
1 marble + 1 bead = 99.40 ÷ 7 = 14.20 --- (4)

Cost of 1 marble and 1 bead = $14.20

(b)
4 marbles + 3 beads = 51.50 --- (2)

(4) _{x 3}
3 marbles + 3 beads = 3 x 14.20 = 42.60 --- (5)

(2) - (5)
4 marbles + 3 beads - 3 marbles - 3 beads = 51.50 - 42.60
4 marbles - 3 marbles + 3 beads - 3 beads = 8.90
1 marble = 8.90

Cost of 1 marble = $8.90

(c)
Substitute 1 marble = 8.90 into (4).

1 marble + 1 bead = 14.20
8.90 + 1 bead = 14.20
1 bead = 14.20 - 8.90 = 5.30

Cost of 1 bead = $5.30

Answer(s): (a) $14.20; (b) $8.90; (c) $5.30