Adam pays $10.10 for 2 stickers and 3 marbles.
A sticker costs $4.30 more than 1 marble.
What is the cost of 4 stickers and 3 marbles?
Choose the cheaper item to be 1 u.
1 sticker costs $4.30 more than 1 marble.
The cheaper item is the marble.

Cost of the marble = 1 u
Cost of the sticker = 1 u + 4.30

Cost of 2 stickers = 2 x (1 u + 4.30) = 2 u + 8.60
Cost of 3 marbles = 3 u

Total cost of 2 stickers and 3 marbles
= 2 u + 8.60 + 3 u
= 2 u + 3 u + 8.60
= 5 u + 8.60

5 u + 8.60 = 10.10
5 u = 10.10 - 8.60
5 u = 1.50

1 u = 1.50 ÷ 5 = 0.30

Cost of 4 stickers and 3 marbles
= 4 x (1 u + 4.30) + 3 u
= 4 u + 17.20 + 3 u
= 4 u + 3 u + 17.20
= 7 u + 17.20
= 7 x 0.30 + 17.20
= 2.10 + 17.20
= $19.30

Answer(s): $19.30