Let's begin by identifying key information given to us:
Length = 12 ft, Width = 18 ft, number of flowers = 32
Area (of rectangular garden) = Length * Width = 12 * 18 = 216 sq ft
Population density = Number of flowers / Area
[tex]\begin{gathered} D=\frac{n}{A}=\frac{32}{216}=0.1482\approx0.15 \\ D=0.15/ft^2 \end{gathered}[/tex]