20) $\frac{45}{8(5-4)-3}$

Step 1 ：Simplify the expression inside the parentheses: \(5 - 4 = 1\)

Step 2 ：Perform the division: \(\frac{45}{8(1) - 3} = \frac{45}{8 - 3} = \frac{45}{5} = 9\)

Step 3 ：Final Answer: \(\boxed{9}\)