In a coconut grove, (x + 4) trees yield 60 nuts per year, x trees yield 120 nuts per year and (x – 4) trees yield 180 nuts per year. If the average yield per year per tree be 100, find x.	Choose the correct choice.
A) 3	B) 4	C) 8	D) 9	E) none of the above

Rationale: ( x + 4 ) × 60 + x × 120 + ( x − 4 ) × 180 / ( x + 4 ) + x + ( x − 4 ) = 100 ⇒ 360 x − 480 / 3 x = 100 ⇒ 60 x = 480 ⇒ x = 8 answer c
Answer: C