Let us say that the sides of the two squares are 'a' and 'b'
Sum of their areas = a^2 + b^2 = 468
Difference of their perimeters = 4a - 4b = 24
=> a - b = 6
=> a = b + 6
So, we get the equation
(b + 6)^2 + b^2 = 468
=> 2b^2 + 12b + 36 = 468
=> b^2 + 6b - 216 = 0
=> b = 12
=> a = 18