Me with this questions and shoe your work. you very much

D
E
F

Work
So the answer to the original problem:
6-4.5 +(-8) equals -1.5
D,E,and F all yeild this answer.

Another way to do it is to simply rearrange the equation 

D:
6-4.5 +(-8)
6-4.5-8
your just removing the parenthesis and swapping the sign

E:
6+(-4.5) -8
is the exact same as
6-4.5 +(-8)
you're just moving the parenthesis

F:
This one you're just adding a parenthesis and flipping the of
6-4.5 +(-8)
which turns it into
6+(-4.5)+(-8)

Hope this helps!