Let's look at the corresponding ratios:
[tex]\frac{AB}{ED}=\frac{24}{30}=\frac{4}{5}\\
\frac{BC}{DC}=\frac{16}{20}=\frac{4}{5}\\
\frac{AC}{EC}=\frac{21}{28}=\frac{3}{4}\\[/tex]
And we see that the three aren't equal.
Hence, $\Delta ABC$ and $\Delta EDC$ are not similar.
