Assuming the question is:
[tex]a=d+\frac{c}{b}[/tex]we need to solve for d.
We keep "d" to one side and simplify the other side for a formula for d. Shown below:
[tex]\begin{gathered} a=d+\frac{c}{b} \\ d=a-\frac{c}{b} \\ d=\frac{ab-c}{b} \end{gathered}[/tex]
