Đáp án:
$\begin{array}{l}
a)\widehat A = \widehat N;\widehat B = \widehat K\\
\Leftrightarrow \Delta ABC = \Delta NKM\\
b)\widehat A = \widehat K;AB = NK\\
\Leftrightarrow \Delta ABC = \Delta KNM\\
c)AC = MN;BC = NK\\
\Leftrightarrow \Delta ABC = \Delta MNK
\end{array}$