How many ounces of a 60% salt solution must be added to 60 ounces of a 20 percent salt solution so that the resulting mixture is 40% salt? Choose the correct choice from the following:
A) 16.67 B) 30 C) 50 D) 60 E) 70

Rationale: "let x = ounces of 60 % salt solution to be added . 2 * 60 + . 6 x = . 4 ( 60 + x ) x = 60 answer d"
Answer: D