A football team has a net yardage of -26 and 1/3 yards.
To get a first down, they need a net yardage of +10.
So in order to get a first down on the next play, they need to make up for the 26 and 1/3 yards, and then an extra 10 yards on top of that.
Thus they need 26 + 1/3 + 10 yards.
Or 36 1/3 yards.