Given:
The mass of the box is,
[tex]m=6\text{ kg}[/tex]The force applied on the box is,
[tex]F=50\text{ N}[/tex]The angle of the force with the horizontal is,
[tex]\theta=53^{\circ}[/tex]The coefficient of friction is,
[tex]\mu=0.3[/tex]The Normal force on the box is,
[tex]\begin{gathered} N=\text{Fsin}\theta-mg \\ =50\times\sin 53^{\circ}-6\times9.8 \\ =-18.9\text{ N} \end{gathered}[/tex]The frictional force on the box is (we take the magnitude of the force only)
[tex]\begin{gathered} f=\mu N \\ =0.3\times18.9 \\ =5.6\text{ N} \end{gathered}[/tex]Hence the frictional force is 5.6 N.