Can you help me subtract intervals? I was reading my abstract math textbook and they subtracted
$[3, 6] - [4, 8) = [3, 4)$. I was wondering if someone could write out how they got to $[3, 4$). I looked at wikipedia and it said I should go 
$[a, b] - [c, d] = [a-d, b-c]$. When I did this, I got $[-5, 2)$. I would be thankful for an explanation-- the book doesn't explain so it's probably really obvious-- but I don't know.

$$[3,6]\setminus[4,8)=([3,4)\cup[4,6])\setminus\left([4,6]\cup(6,8)\right)$$
$$=[3,4)\setminus(6,8)$$
$$=[3,4)$$
