The first thing we must do for this case is to define variables.
We have then:
x: weight of the big box
y: weight of the small box.
We now write the system of equations that models the problem:

We apply the graphic solution.
For this, the solution will be the cut point of both lines.
We have then that the solution occurs for the point:
Note: see attached image
Answer:
Weight of each large box: 15.5 Kilograms
Weight of each small box: 13.25 Kilograms
I got:
-2(2f-3g)
explanation:
used communicative property
Answer:
around 35-42° it's one of them 2 probably 40-41°