Given data:
The given figure of the triangle and rectangle.
The perimeter of the triangle is,
[tex]\begin{gathered} P=1.5e+4.5e+5.1f \\ =6e+5.1f \end{gathered}[/tex]The perimeter of rectangle is,
[tex]\begin{gathered} P^{\prime}=2(\text{1}.5e+4.5f) \\ =3e+9f \end{gathered}[/tex]The difference in the perimeter of recatngle and triangle is,
[tex]\begin{gathered} P^{\prime}-P=3e+9f-(6e+5.1f) \\ =-3e+3.9f \end{gathered}[/tex]Thus, the third option is correct.