Answer :
The given equation is
[tex]u=y+\frac{k}{x}[/tex]First, let's subtract y from each side.
[tex]\begin{gathered} u-y=y-y+\frac{k}{x} \\ u-y=\frac{k}{x} \end{gathered}[/tex]Then, we multiply x on each side.
[tex]\begin{gathered} x(u-y)=x\cdot\frac{k}{x} \\ x(u-y)=k \end{gathered}[/tex]At last, let's divide each side by u-y.
[tex]\begin{gathered} \frac{x(u-y)}{u-y}=\frac{k}{u-y} \\ x=\frac{k}{u-y} \end{gathered}[/tex]