The sum of two vectors is always $\vec{A}+\vec{B}$.

For example: if $\vec{B}=-0.2 \vec{A}$
$\vec{A}+\vec{B}=\vec{A}+ (-0.2\vec{A})=0.8 \vec{A}$ (1.0-0.2)

if$\vec{B}= 0.2 \vec{A}$ , two vector are parallel.
$\vec{A}+\vec{B}=\vec{A}+ (0.2\vec{A})=1.2 \vec{A}$ (1.0+0.2)