If Adam buys 3 stickers and 4 marbles, it costs $50.30.
If Adam buys 4 stickers and 3 marbles, he will have $5.40 left.

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)
3 stickers + 4 marbles = 50.30 --- (1)
4 stickers + 3 marbles = 50.30 - 5.40 = 44.90 --- (2)

(1) + (2)
7 stickers + 7 marbles = 95.20 --- (3)

(3) _{÷ 7}
1 sticker + 1 marble = 95.20 ÷ 7 = 13.60 --- (4)

Cost of 1 sticker and 1 marble = $13.60

(b)
(4) _{x 3}
3 stickers + 3 marbles = 3 x 13.60 = 40.80 --- (5)

(2) - (5)
4 stickers + 3 marbles - 3 stickers - 3 marbles = 44.90 - 40.80
4 stickers - 3 stickers - 3 marbles + 3 marbles = 4.10
1 sticker = 4.10

Cost of 1 sticker = $4.10

(c)
Substitute 1 sticker = 4.10 into (4).

1 sticker + 1 marble = 13.60
4.10 + 1 marble = 13.60
1 marble = 13.60 - 4.10 = 9.50

Cost of 1 marble = $9.50

Answer(s): (a) $13.60; (b) $4.10; (c) $9.50