The answer is -11.25.
To solve this, let's first get everything to a decimal. This will make things easier.
(4.5 - 11.25) - 9/2
(4.5 - 11.25) - 4.5
Now because of the properties of addition and subtraction, we can remove the parenthesis.
4.5 - 11.25 - 4.5
And when we complete this operation, the 4.5 and -4.5 cancel, giving us just -11.25