I think the easiest thing to do is to write it like this:
[tex] {f}^{8} \times {f}^{11} \times -11 \times 3 [/tex]
Then
[tex] {f}^{8} \times {f}^{11} = {f}^{19} .[/tex]
and
[tex]-11 \times 3 = -33.[/tex]
Which leaves you with
[tex] {f}^{19} \times -33 = -33 {f}^{19} .[/tex]
