2. (3 points) $199772 \times 199911-199771 \times 199912=$
【Solution】Solution: $199772 \times 199911-199771 \times 199912$,
$$
\begin{array}{l}
=199772 \times 199911-199771 \times(199911+1), \\
=199772 \times 199911-199771 \times 199912-199771, \\
=199911 \times(199772-199771)-199771, \\
=199911-199771 \\
=140 .
\end{array}
$$

The answer is: 140 .