The area of a square is 18 sq in less than twice the area of a triangle. the base of the triangle is 3 in longer and the altitude is the same length as the side of the square

Let the side of the square = x

So, the altitude of the triangle = x

and it's base = x+3

2 (area of triangle) - 18 = area of the square

area of the triangle = (1/2) height * base

and

area of the square = side^2

{ (2) (1/2) (x) (x+3) } - 18 = x^2

x^2 + 3 x - 18 = x^2

3x - 18 = 0

3x = 18

x = 6

so, the length of one side of the square = 6 units = altitude of the triangle

and the base of the triangle = 6 + 3 = 9cm.