$\displaystyle f(x)=3^x$ $\displaystyle g(x)=x+2$ $\displaystyle h(x)=2x-3$ which i need to arrange to get $\displaystyle y=\frac{1}{27}*3^{2x}+2$

i can get the last part of the equation when i do $\displaystyle g*f(x+3)*h(x)$ but not sure where the fraction comes from