Respuesta :
when you have minus negative it is the same result as plus positive, so 3+4 is what you're looking for
[tex] \bf 3-(-4)~~
\begin{cases}
-(-4)=-1(-4)\\
\qquad\qquad -1\cdot -4\\
\qquad\qquad +4
\end{cases}~\hspace{8em} 3+4 [/tex]