Answer
$$7 + 9i$$
Work Step by Step
$$\eqalign{
& {\text{Let }}{\bf{u}} = 7 + 6i,{\text{ and }}{\bf{v}} = 3i \cr
& {\text{Find the sum }}{\bf{u}} + {\bf{v}} \cr
& {\bf{w}} = {\bf{u}} + {\bf{v}} \cr
& {\bf{w}} = \left( {7 + 6i} \right) + \left( {3i} \right) \cr
& {\bf{w}} = 7 + 6i + 3i \cr
& {\text{Add imaginary parts}} \cr
& {\bf{w}} = 7 + 9i \cr
& \cr
& {\text{Graph}} \cr} $$
