-18 - (9 - 5) - 0.25 - (-2.25)

First, solve the expression within the parentheses:

9 - 5 = 4

Now the expression becomes:

-18 - 4 - 0.25 - (-2.25)

Next, solve the expression within the second set of parentheses by making the negative sign in front of -2.25 into a positive sign:

-18 - 4 - 0.25 + 2.25

Now combine like terms:

-18 - 4 - 0.25 + 2.25 = -20

Therefore, the final answer is:

-20