#### Answer

a) $x=\dfrac{C-B}{A}$
b) $A=\dfrac{C-B}{x}$

#### Work Step by Step

a) Using the properties of equality, in terms of $
x
,$ the given formula, $
Ax+B=C
,$ is equivalent to
\begin{array}{l}\require{cancel}
Ax=C-B
\\\\
x=\dfrac{C-B}{A}
.\end{array}
b) Using the properties of equality, in terms of $
A
,$ the given formula, $
Ax+B=C
,$ is equivalent to
\begin{array}{l}\require{cancel}
Ax=C-B
\\\\
A=\dfrac{C-B}{x}
.\end{array}