In a coconut grove, (x + 3) trees yield 60 nuts per year, x trees yield 120 nuts per year and (x – 3) trees yield 180 nuts per year. If the average yield per year per tree be 100, find x.	Answers
A) 3  B) 4  C) 5  D) 6  E) none of the above

Rationale: "( x + 3 ) × 60 + x × 120 + ( x − 3 ) × 180 / ( x + 3 ) + x + ( x − 3 ) = 100 ⇒ 360 x − 360 / 3 x = 100 ⇒ 60 x = 360 ⇒ x = 6 answer d"
Answer: D