13. \(4\frac{1}{4}-(2\frac{1}{2}+1\frac{3}{8})\)

\[2\frac{1}{2}+1\frac{3}{8}=\frac{20}{8}+\frac{11}{8}=\frac{31}{8}\]

\[4\frac{1}{4}-\frac{31}{8}=\frac{34}{8}-\frac{31}{8}=\frac{3}{8}\]

Ответ: \(\frac{3}{8}\).