Answer
$y=Cx$
Work Step by Step
We know that $\log_a {x}+\log_a {y}=\log_a {(x\cdot y)}$.
Hence,
$\ln{x}+\ln{C}\\=\ln{(x\cdot C)}=\ln{(Cx)}$
Thus, the given equation is equivalent to
$\ln{y} = \ln{(Cx)}$
Use the rule $\log_a{M}=\log_a{N} \longrightarrow M=N$ to obtain
$y=Cx$