If m= c*a*b/a-d         then b equals.      

Dear student,
Here is the solution of your asked query:

$$\begin{gathered} m=\frac{c\times a\times b}{a-d} \\ \Rightarrow m\left(a-d\right)=c\times a\times b \\ \Rightarrow b=\frac{m\left(a-d\right)}{c\times a} \end{gathered}$$
Regards