#### Answer

$d=2Q-c$

#### Work Step by Step

$\bf{\text{Solution Outline:}}$
To solve the given equation, $
Q=\dfrac{c+d}{2}
$ for $
d
,$ use the properties of equality to isolate the variable.
$\bf{\text{Solution Details:}}$
Using the properties of equality to isolate the variable, the equation above is equivalent to
\begin{array}{l}\require{cancel}
Q=\dfrac{c+d}{2}
\\\\
2\cdot Q=2\cdot\dfrac{c+d}{2}
\\\\
2Q=c+d
\\\\
2Q-c=d
\\\\
d=2Q-c
.\end{array}