Решение:
- \( 3\frac{1}{2} = \frac{7}{2} \)
- \( 1\frac{11}{20} = \frac{31}{20} \)
- \( \frac{7}{2} - \frac{31}{20} = \frac{70}{20} - \frac{31}{20} = \frac{39}{20} \)
- \( 19\frac{1}{2} = \frac{39}{2} \)
- \( \frac{39}{2} \cdot \frac{39}{20} = \frac{1521}{40} \)
- \( \frac{111}{200} : \frac{3}{20} = \frac{111}{200} \cdot \frac{20}{3} = \frac{111}{10} \cdot \frac{1}{3} = \frac{37}{10} \)
- \( \frac{1521}{40} - \frac{37}{10} = \frac{1521}{40} - \frac{148}{40} = \frac{1373}{40} \)
Ответ: \(\frac{1373}{40}\)