[tex]8f+7-2f=16\\6f=16-7\\6f=9\\f=\frac{9}{6}[/tex]
We know f, now we want the 12f+1
Therefore, Substitute f = 9/6 in 12f+1
[tex]12(\frac{9}{6})+1\\ = 2*9+1\\=18+1\\=19[/tex]
If you are wondering where 2*9 comes from, it comes from the 12(9/6) and 12 is divided by 6 then we get 2 and multiply the 9 as we get 2*9.