Answer
$\begin{aligned} & F_{A C}=85.8 \mathrm{~N} \\ & F_{A B}=578 \mathrm{~N} \\ & F_{A D}=565 \mathrm{~N}\end{aligned}$
Work Step by Step
Equations of Equilibrium.
$
\begin{aligned}
& \Sigma F_x=0 ; F_{A B}\left(\frac{4}{\sqrt{57}}\right)-F_{A C}\left(\frac{2}{\sqrt{38}}\right)-F_{A D}\left(\frac{4}{\sqrt{66}}\right)=0 \\
& \Sigma F_y=0 ; F_{A B}\left(\frac{4}{\sqrt{57}}\right)+F_{A C}\left(\frac{3}{\sqrt{38}}\right)-F_{A D}\left(\frac{5}{\sqrt{66}}\right)=0 \\
& \Sigma F_z=0 ;-F_{A B}\left(\frac{5}{\sqrt{57}}\right)-F_{A C}\left(\frac{5}{\sqrt{38}}\right)-F_{A D}\left(\frac{5}{\sqrt{66}}\right)+800
\end{aligned}
$
After Solving Eqs
$
\begin{aligned}
& F_{A C}=85.77 \mathrm{~N}=85.8 \mathrm{~N} \\
& F_{A B}=577.73 \mathrm{~N}=578 \mathrm{~N} \\
& F_{A D}=565.15 \mathrm{~N}=565 \mathrm{~N}
\end{aligned}
$
