Given:
The cost of mulch per bag, C=$3.75.
The area covered by each bag, a=18 sq. ft.
The base length of triangular- shaped garden , b=12 ft.
The altitude of triangular- shaped garden , h=7.1 ft.
Now, the area of the triangular-shaped garden can be calculated as,
[tex]\begin{gathered} A=\frac{1}{2}bh \\ =\frac{1}{2}\times12\times7.1 \\ =42.6\text{ sq ft} \end{gathered}[/tex]Now, the number of bags of mulch needed for the triangular- shaped garden is,
[tex]\begin{gathered} n=\frac{A}{a} \\ =\frac{42.6}{18} \end{gathered}[/tex]The total cost of bags of mulch needed for the triangular- shaped garden is,
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