Idon’t understand geometry and need doing this.

It would be 15 m how i got the answer: (20x20) + b^2 = (25x25)400 + b^2 = 625625-400=225square that and get 15hope this : )

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.