Let Site A's 2023 amount be $x$, so Site B's 2023 amount is $100-x$. Use the two different 2024 percentage changes to create an equation with total $103$.

After finding each site's 2024 amount, apply the 2025 percentage change to that site's 2024 amount, not to its 2023 amount.

Algebra is the fastest approach because the 2024 combined total directly determines the 2023 split. Desmos can quickly verify that split.

Enter $y=1.18x+0.93(100-x)$ and $y=103$. Click their intersection to find Site A's 2023 amount when the 2023 total is $100$.

Using the intersection's $x$-coordinate, enter $0.85(1.18x)+1.08(0.93(100-x))-100$. Because the starting total was $100$, this result is the percentage increase from 2023 to 2025.

Let the combined number of boxes in 2023 be $100$. If Site A distributed $x$ boxes, then Site B distributed $100-x$ boxes.

The 2024 combined total was $103$, since it was 3% greater than $100$. Therefore,

Solving gives $0.25x=10$, so $x=40$. Thus, in 2023, Site A distributed $40$ boxes per 100 total boxes and Site B distributed $60$ boxes per 100 total boxes.

In 2024, the sites distributed $1.18(40)=47.2$ and $0.93(60)=55.8$ boxes, respectively, per 100 original boxes.

For 2025, the combined total is

Compared with the 2023 total of $100$, this is an increase of $0.384$ per 100, or $0.384\%$.