70% is not equivalent but 60% is
She bought 7 paintbrushes
3.85/ 0.55= 7
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
Answer:
£12 per hour
Step-by-step explanation:
7 × 5 = 35 hours
35 h : 420
1 h : x
x = 420×1 / 35
= £12 per hour