If Adam buys 2 stickers and 3 marbles, it costs $23.70.
If Adam buys 3 stickers and 2 marbles, he will need another $3.10.

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

(a)
2 stickers + 3 marbles = 23.70 --- (1)
3 stickers + 2 marbles = 23.70 + 3.10 = 26.80 --- (2)

(1) + (2)
5 stickers + 5 marbles = 50.50 --- (3)

(3) _{÷ 5}
1 sticker + 1 marble = 50.50 ÷ 5 = 10.10 --- (4)

Cost of 1 sticker and 1 marble = $10.10

(b)
3 stickers + 2 marbles = 26.80 --- (2)

(4) _{x 2}
2 stickers + 2 marbles = 2 x 10.10 = 20.20 --- (5)

(2) - (5)
3 stickers + 2 marbles - 2 stickers - 2 marbles = 26.80 - 20.20
3 stickers - 2 stickers + 2 marbles - 2 marbles = 6.60
1 sticker = 6.60

Cost of 1 sticker = $6.60

(c)
Substitute 1 sticker = 6.60 into (4).

1 sticker + 1 marble = 10.10
6.60 + 1 marble = 10.10
1 marble = 10.10 - 6.60 = 3.50

Cost of 1 marble = $3.50

Answer(s): (a) $10.10; (b) $6.60; (c) $3.50