$R_x=\sum F_x=20\ N\ (\rightarrow)$

$R_y=\sum F_y=50-60=-10\ N=10\ N(\downarrow)$

$R=\sqrt{R_x^2+R_y^2}=22.36\ N$

$\theta =tan^{-1}\Bigg(\dfrac{R_y}{R_x}\Bigg)=26.56^o$

Using Varignon's Theorem

$\sum M_c=M_c^R..............(i)$

$\sum M_c=-20(1)-50(9)+60(2)=-350\ N.m$

Considering point C as origin, 

$x-intercept=\dfrac{\sum M_c}{R_y}=35\ m$

$y-intercept=\dfrac{\sum M_c}{R_x}=17.5\ m$