Tobias brought some money out for shopping to prepare for his backpack travelling this December. He spent 3/7 of his money on a backpack and 2/3 of the remaining amount of money on 3 identical purification bottles. He spent the rest of his money on 3 travel first aid kits. The cost of a purification bottle is $14.80 more than the cost of each first aid kit. How much money did Tobias spend on the backpack and purification bottles altogether?
Call the total amount of money that he has at first = M
The backpack costs (3/7)M
The amount that remains = (4/7)M
(2/3) of this = (2/3)(4/7)M = (8/21)M = money spent on purification bottles
Money spent of first aid kits = (M - 3/7 M - 8/21 M ) = (4/21)M
Note that the total difference between the cost of the purification bottles and the first aid kits = 3 (14.80)
So
(8/21)M - (4/21) M = 3 (14.80)
(4/21)M = 44.40
M = 44.4 *(21/4) ≈ $233.10
Amt spent on backpack ≈ (3/7)(233.10) ≈ $99.90
Amt spent on purification bottles = (8/21)(233.10) ≈ $88.80