Adam pays $19.30 for 3 marbles and 2 beads.
A marble costs $3.60 more than 1 bead.
What is the cost of 2 marbles and 4 beads?
Choose the cheaper item to be 1 u.
1 marble costs $3.60 more than 1 bead.
The cheaper item is the bead.

Cost of the bead = 1 u
Cost of the marble = 1 u + 3.60

Cost of 3 marbles = 3 x (1 u + 3.60) = 3 u + 10.80
Cost of 2 beads = 2 u

Total cost of 3 marbles and 2 beads
= 3 u + 10.80 + 2 u
= 3 u + 2 u + 10.80
= 5 u + 10.80

5 u + 10.80 = 19.30
5 u = 19.30 - 10.80
5 u = 8.50

1 u = 8.50 ÷ 5 = 1.70

Cost of 2 marbles and 4 beads
= 2 x (1 u + 3.60) + 4 u
= 2 u + 7.20 + 4 u
= 2 u + 4 u + 7.20
= 6 u + 7.20
= 6 x 1.70 + 7.20
= 10.20 + 7.20
= $17.40

Answer(s): $17.40