To solve this plug 2 in for d in the equation like so:

The fraction
can be simplified to 2.
How I found this:
The greatest common factor of 8 and 4 is 4.
If we divide 8 by 4 you get 2
If you divide 4 by 4 you would get 1
That gives you the simplified fraction:
Which is the same as simply 2
Now we have the expression:
2 - 2
^^^ A number subtracted from itself is always zero
The answer is:
0
Hope this helped!
~Just a girl in love with Shawn Mendes