Nora tried to evaluate an expression step by step.
$\qquad\begin{align}
&1539 \div 3\\\\
\\
=&(1500 \div 3) + (30 \div3) + (9 \div3)&\greenD{\text{Step } 1}\\\\
\\
=&500 + 10 + 3&\blueD{\text{Step } 2}\\\\
\\
=&513&\purpleC{\text{Step } 3} \\\\
\end{align}$
**Find Nora's mistake.**
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