In the figure below, the sum of the sides of square a and square B is 20 cm. Square a is 40 cm larger than square B

In the figure below, the sum of the sides of square a and square B is 20 cm. Square a is 40 cm larger than square B

This is the transformation of a quadratic equation of two variables
Let the length of side a be xcm and the length of side B be YCM
x+y=20 (1)
x2-y2=40 (2)
Add (1) square and (2) to get:
Extracting common factor by 2 x2 + 2XY = 440
X(x+y)=220
We get x = 11, y = 9