Frank is making salad dressing for a large party. If a serving is 2 1/2 tablespoons, how many servings can he make with 85 tablespoons?

To determine the number of servings Frank can make, divide the total number of tablespoons by the serving size: 85 tablespoons / 2.5 tablespoons/serving = <<85/2.5=34>>34 servings. Answer: \boxed{34}.