explain preparation of aryl halides from benzene, alkyle benzene and benzene diazonium chloride

Dear Student,

Aryl halides can be prepared from benzene by electrophilic aromatic substitutionnof benzene. This is carried out by the reaction of benzene with halogen in presence of lewis acid. 
${\mathrm{C}}_6{\mathrm{H}}_6 +\hspace{0.17em}{\mathrm{X}}_2 \stackrel{{\mathrm{AlCl}}_3}{\to } {\mathrm{C}}_6{\mathrm{H}}_5\mathrm{X} + \mathrm{HX}$

From diazonium salts, they can be prepared by Sandmeyer reaction.