Выполним действия по порядку:
1) \(\frac{17}{18} - \frac{5}{12} = \frac{17 \cdot 2}{18 \cdot 2} - \frac{5 \cdot 3}{12 \cdot 3} = \frac{34}{36} - \frac{15}{36} = \frac{34 - 15}{36} = \frac{19}{36}\)
2) \(\frac{19}{36} : \frac{4}{9} = \frac{19}{36} \cdot \frac{9}{4} = \frac{19 \cdot 9}{36 \cdot 4} = \frac{19 \cdot 1}{4 \cdot 4} = \frac{19}{16}\)
3) \(36 \cdot \frac{19}{16} = \frac{36 \cdot 19}{16} = \frac{9 \cdot 19}{4} = \frac{171}{4} = 42.75\)
Ответ: 42.75