Question 2444
Let side of square be x

so, area of square = x^2

Rectangle will have length = x+10 and width = x+5

so, area of rectangle = (x+10)(x+5)

We are told that rectangle area = 3(square area), so...

(x+10)(x+5) = 3x^2
x^2 + 15x + 50 = 3x^2
2x^2 - 15x - 50 = 0
(2x + 5)(x - 10) = 0

so 2x+5=0 OR x-10=0

x=-5/2 or x=10

Physically, x=10m.

jon