Hey there!☺
[tex]Answer:\boxed{a=k+u}[/tex]
[tex]Explanation:[/tex]
Solve for a: [tex]u=a-k[/tex]
Let's start by flipping the equation.
[tex]a-k=u[/tex]
Now add k to both sides.
[tex]a-k+k=u+k\\a=k+u[/tex]
[tex]a=k+u[/tex] is your final answer.
Hope this helps!