Given:
[tex]\begin{gathered} f(a)=a+2 \\ g(a)=a^2-3a \end{gathered}[/tex]The objective is to find (f o g)(a).
The required operation can be calculated as,
[tex]\begin{gathered} (f\circ g)(x)=f(g(x)) \\ =f(a^2-3a) \\ =a^2-3a+2 \end{gathered}[/tex]Hence, the the result of (f o g)(a) is obtained.