when we resolve the angle the force F makes with the horizontal we get Fcos60° is the force that keeps the block in equilibrium against the 100N force
so
100N= Fcos°60
100N=F/2
Therefore
F=200N
The normal force or normal reaction is again got got by resolving F
Nr =Fsin60°(where Nr is the normal reaction)
Nr=200(√3)/2
Nr=100(√3)N