I've heard 90%/10%. But I think it varies. If you exercise more and burn more calories, obviously it counts for a larger percentage of your loss. Also, I think exercise becomes more important as you go along... as you lose weight, your calorie needs lower, and you can only cut your food intake so far, so exercise can make up the difference.
I think the point of those percentages is just to show that what you eat has more of an effect on your weight than the exercise you do, because you can eat in a few minutes something that takes an hour to burn off or more.
