Answer
a). $4x+2y$
b). Magnitude $\approx4.5$,
Angle$=26.6^{\circ}$ with the OX-axis.
Work Step by Step
a). vec(A)=3x+5y, vec(B)=1x-3y,
vec(A)+vec(B)=4x+2y
b). So, Magnitude of vec(A)+vec(B)=$\sqrt (4^{2}+2^{2})\approx4.5$
Angle$=\theta=tan^{-1}\frac{2}{4}=26.6^{\circ}$
