And can you plz explain it to me

It's the one on the bottom left that says 5ft and 3ft, they're the same shape and ratio just turned around. It's also the square that says 6ft and 10ft because its only two times bigger than the original and has similar proportions.

So it’s pretty easy actually all you have to do is for instance all you have to do is if one shape has 3 feet on one side in another shape has 3 feet on the same side that the other shape does that goes in the similar in the other box which is not similar like if The numbers have a significant difference in that goes in the summer the last box in the middle box are the ones that for instance if it’s 3 feet and 5 feet that goes in the middle box. I hope that helps!