Given the equation:
[tex]f-(-4)=12[/tex]The first thing to do is get rid of the parenthesis, since there is a negative sign outside of them, the content will change it's sign:
[tex]\begin{gathered} f-(-4)=12 \\ \Rightarrow f+4=12 \end{gathered}[/tex]Now, we pass the 4 to the other side of the equation changing it's sign again:
[tex]\begin{gathered} f+4=12 \\ \Rightarrow f=12-4=8 \\ f=8 \end{gathered}[/tex]therefore, f=8
