20. (6 points) This year is 2015, Xiao Ming says: “My current age is exactly the same as the sum of the four digits of the year I was born,” then Xiao Ming is $\qquad$ years old.
【Solution】Solution: Assume Xiaoming was born 2000 years ago, let the birth year be $19xy$, according to the problem we have:
$$
\begin{array}{c}
2015-(1900+10x+y)=1+9+x+y \\
115-10x-y=10+x+y \\
11x+2y=105
\end{array}
$$

Since $x$ and $y$ are single digits, solving gives: $x=9, y=3$
So Xiaoming was born in 1993, and his age this year is: $1+9+9+3=22$ (years old)
Assume Xiaoming was born after 2000, let the birth year be 20xy, $x$ must be less than 2, according to the problem we have:
$$
\begin{array}{c}
2015-(2000+10x+y)=2+0+x+y \\
15-10x-y=2+x+y \\
11x+2y=13
\end{array}
$$

Since $x$ and $y$ are single digits, solving gives: $x=1, y=1$
So Xiaoming was born in 2011, and his age this year is: $2+0+1+1=4$ (years old)
Answer: Xiaoming is 22 years old or 4 years old this year.
Therefore, the answer is: 22 or 4.