# How do you solve f+(-3)=-9?

Add $\textcolor{red}{3}$ to each side of the equation to solve for $f$ while keeping the equation balanced:
$f + \left(- 3\right) + \textcolor{red}{3} = - 9 + \textcolor{red}{3}$
$f + 0 = - 6$
$f = - 6$