Hint 1 - From looking at B’s description, you can see the match boxes are long, therefore you can narrow down which side B is looking at the boxes.

 

Hint 2 - With the knowledge that B can only be viewing the matches from two sides, you can multiply each pile with the layers with one of the sides (you may need a piece of paper).

 

Hint 3 - Once you multiplied each of the layers and piles, add them up and this should give you the total number from that perspective. Now do this for the other possible side, remember we want the maximum number of match boxes.

The maximum total number of matches is 21! By multiplying each pile with each layer and then adding them up, you can work out which side has the maximum number of matches. I hope you enjoyed this little brain teaser and I’ll see you again for the final puzzle of the series!