Missing info: The width of the patio is 3/4 its length.
Given:
Area = 432 square feet.
length = x
width = 3/4 x
Area of a rectangle = Length width
432 ft² = x 3/4 x
432 ft²/3/4 = x²
432 ft² 4/3 = x²
576 = x²
√576 = √x²
24 = x
Length is 24 ft.
Width = 3/4 24ft
Width = (3*24)/4
Width = 72/4
Width = 18 ft.