We can combine 19t and -6t. When we subtract these from each other, we get the following: 19t - 6t = 13t (If you don't understand this, you can see it as a story -- You have 19 apples (19a) and subtract 6 apples (6a), what's left? Answer 13t)
We can't add the seperate number (8) to this 13t, so it rests "free-standing" Hence, 8 + 13t
