I actually did this kind of question earlier today in a math contest. It took me a while to get it, but it was quite easy.

So we basically know that:

\( A+B+C=75 \)

Now here comes the tricky part. We have to determine how many rocks there are in each box.

The easy thing about this is that we already know what will be in the boxes after the movements. It’s just \( 75÷3 \).

So now we know, that after the movements, each of the boxes will contain 12.

Lets do the operations on the boxes.

\( A-28+19=25 \)

\( B-24+28=25 \)

\( C-19+24=25 \)

And we find that:

\( A=34 \)

\( B=21 \)

\( C=20 \)

And from that, we get:

\( A=34 \)

! Enjoy.

~Cam943, Junior Moderator

The random A and a triangle next to 75 is supposed to be a division sign.

How did u get 34 and 21 and 20.

It explains in the answer. 34, 21 and 20 add up to 75

I’m sorry! It is supposed to say that each of the boxes will contain 25.