Frank tried to solve an equation step by step.
$\qquad\begin{align}
-5&=5(d+4)\\\\
\\
-5&=5d+20&\green{\text{Step } 1}\\\\
\\
15&=5d&\blue{\text{Step } 2}\\\\
\\
3&=d&\purple{\text{Step } 3}\\\\
\end{align}$
**Find Frank's mistake.**
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