## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$a=\dfrac{c}{3+b+d}$
Using the properties of equality, in terms of $a$, the given expression, $3a=c-a(b+d)$, is equivalent to \begin{array}{l} 3a=c-ab-ad \\\\ 3a+ab+ad=c \\\\ a(3+b+d)=c \\\\ a=\dfrac{c}{3+b+d} .\end{array}