So:
Let us simply the parenthesis first.
So we have [tex]\sf{(8-6x+12)}[/tex]
We can rearrange the terms and get:
[tex]\sf{(8+12-6x)}[/tex]
Which is equal to
[tex]\sf{(20-6x)}[/tex]
So now we have to complete it by multiplying it all by 1/4 which is basically dividing it by 4.
So:
[tex]\sf{\frac{20-6x}{4}}[/tex]
Simplifying that, we get:
[tex]\sf{5-\frac{6}{4}x}[/tex]
And reducing that farther we finally get:
[tex]\sf{5-\frac{3}{2}x}[/tex]
Which is your final answer :)