Adam pays $5.30 for 2 marbles and 3 beads.
A marble costs $1.90 more than 1 bead.
What is the cost of 4 marbles and 3 beads?
Choose the cheaper item to be 1 u.
1 marble costs $1.90 more than 1 bead.
The cheaper item is the bead.

Cost of the bead = 1 u
Cost of the marble = 1 u + 1.90

Cost of 2 marbles = 2 x (1 u + 1.90) = 2 u + 3.80
Cost of 3 beads = 3 u

Total cost of 2 marbles and 3 beads
= 2 u + 3.80 + 3 u
= 2 u + 3 u + 3.80
= 5 u + 3.80

5 u + 3.80 = 5.30
5 u = 5.30 - 3.80
5 u = 1.50

1 u = 1.50 ÷ 5 = 0.30

Cost of 4 marbles and 3 beads
= 4 x (1 u + 1.90) + 3 u
= 4 u + 7.60 + 3 u
= 4 u + 3 u + 7.60
= 7 u + 7.60
= 7 x 0.30 + 7.60
= 2.10 + 7.60
= $9.70

Answer(s): $9.70