2 stickers and 1 marble cost $12.70.
1 sticker and 2 marbles cost $11.60.

1. Find the cost of 1 sticker and 1 marble.
2. Find the cost of 1 marble.
3. Find the cost of 1 sticker.
4. Find the cost of 6 stickers and 6 marbles.

(a)
2 stickers + 1 marble = 12.70 --- (1)
1 sticker + 2 marbles = 11.60 --- (2)

(1) + (2)
3 stickers + 3 marbles = 12.70 + 11.60
3 stickers + 3 marbles = 24.30 --- (3)

(3) _{÷ 3}
3 stickers + 3 marbles = 24.30
1 sticker + 1 marble = 24.30 ÷ 3 
1 sticker + 1 marble = 8.10 --- (4)

Cost of 1 sticker and 1 marble = $8.10

(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 11.60 - 8.10
1 sticker - 1 sticker + 2 marbles - 1 marble = 3.50
1 marble = 3.50

Cost of 1 marble = $3.50

(c)
Substitute 1 marble = 3.50 into (4).
1 sticker + 1 marble = 8.10
1 sticker + 3.50 = 8.10
1 sticker = 8.10 - 3.50 = 4.60

Cost of 1 sticker = $4.60

(d)
(4) _{x 6}
1 sticker + 1 marble = 8.10
6 x (1 sticker + 1 marble) = 6 x 8.10
6 stickers + 6 marbles = 48.60

Cost of 6 stickers and 6 marbles = $48.60

Answer(s): (a) $8.10; (b) $3.50; (c) $4.60; (d) $48.60