11. (8 points) This year, Xiaochun is 18 years younger than his brother. In 3 years, Xiaochun's age will be half of his brother's age. How old is Xiaochun this year? $\qquad$ years old.
【Answer】Solution: $18 \div(2-1)-3$
$$
\begin{array}{l}
=18-3 \\
=15 \text { (years old) }
\end{array}
$$

Answer: Xiaochun is 15 years old this year.
Therefore, the answer is: 15.