Here,
#color(red)(f(x)=2x+1...to(1) and g(x)=x-3....to(2)#
We assume that , #R_fsube D_g and gof # exist.
#gof(x)=g(f(x))#
#color(white)(gof(x))=g(2x+1)#....#color(red)(touse (1)#
#color(white)(gof(x))=g(m)#.....where , #color(blue)(m=2x+1#
#color(white)(gof(x))=m-3#.....#color(red)(touse(2)#
#color(white)(gof(x))=(2x+1)-3#,,,,,where , #color(blue)(m=2x+1#
#color(white)(gof(x))=2x-2#
#gof(x)=2(x-1)#
Answer :#color(orange)((2))x+color(orange)((-2))#