No definitions of the three functions have been provided, so an example will be used for illustration purposes.
f(x)=x+3, g(x)=x-3, h(x)=3x2.
gf(x)=fg(x)=f(x)*g(x)=x2-9.
h୦g(x)=h(g(x))=h(x-3)=3(x-3)2=3x2-18x+27.
h(gf(a))=h(a2-9)=3(a2-9)2=3a4-54a2+243.
h୦g(f(a))=h୦g(a+3)=3(a+3)2-18(a+3)+27=
3a2+18a+27-18a-54+27=3a2.