so the initial equations are:
[tex]\begin{gathered} f(x)=x^2+11x+18 \\ g(x)=x+2 \end{gathered}[/tex]the we can substract theme like:
[tex]\begin{gathered} f(x)-g(x)=x^2+11x+18-(x+2) \\ f(x)-g(x)=x^2+11x+18-x-2 \end{gathered}[/tex]and finally we can simplify it so:
[tex]f(x)-g(x)=x^2-10x+16[/tex]