Answer :
The perimeter of a rectangle is given by the formula:
[tex]\text{Perimeter}=2\cdot\text{length}+2\cdot\text{width}[/tex]If the perimeter is 43.8 and the length is 12.4, we can find the width:
[tex]\begin{gathered} 43.8=2\cdot12.4+2\cdot\text{width} \\ 2\cdot\text{width}=43.8-24.8 \\ 2\cdot\text{width}=19 \\ \text{width}=\frac{19}{2}=9.5 \end{gathered}[/tex]The width is 9.5 feet, therefore the answer is C.