quadratic equations

Let the side of first square is x and the side of second square is y

so 4x - 4y = 64

or x - y = 16

x = 16+ y

and as we know that the sum of the areas of both the triangles = 640

x² + y² = 640

Put x = 16+y

(16+y)² + y² = 640

2y²+32y - 384 = 0

y² + 16y -192 = 0

(y+24)(y-8) = 0

y = -24 or 8 (rejecting negative value)

y = 8m

so x = 16+y

= 16+8

=24m