7. (10 points) Calculate: $1987 \times 2015 - 1986 \times 2016=$
【Analysis】Simplify the calculation according to the distributive law of multiplication.
【Solution】Solution: $1987 \times 2015-1986 \times 2016$
$$
\begin{array}{l}
=1987 \times(2016-1)-1986 \times 2016 \\
=1987 \times 2016-1987-1986 \times 2016 \\
=(1987-1986) \times 2016-1987 \\
=2016-1987 \\
=29 ;
\end{array}
$$

Therefore, the answer is: 29