Answer
$\mu_s=0.591$
Work Step by Step
We have $$f_s=\mu_sF_N$$
The normal force $F_N$ here is the y-component of the force the ground exerts on the ladder $G$, so $$f_s=\mu_sG_y$$
Because the ladder does not slip horizontally, $f_s$ balances $G_x$, so $$f_s=G_x$$ $$\mu_sG_y=G_x$$ $$\mu_s=\frac{G_x}{G_y}=\frac{727N}{1230N}=0.591$$
