3⋅1,5 + \left( \frac{9}{4} - \frac{5}{6} \right) : \frac{1}{9 + 8}

To solve this expression, we first simplify the terms inside the parentheses:

= 4,5 + \left( \frac{54}{24} - \frac{20}{24} \right) : \frac{1}{17}

= 4,5 + \left( \frac{34}{24} \right) : \frac{1}{17}

= 4,5 + \frac{34}{24} \cdot \frac{17}{1}

= 4,5 + \frac{34 \cdot 17}{24}

= 4,5 + \frac{578}{24}

= 4,5 + 24,08

= 28,58

Therefore, the final result is 28,58.