In a coconut grove, (x + 2) trees yield 40 nuts per year, x trees yield 120 nuts per year and (x – 2) trees yield 180 nuts per year. If the average yield per year per tree be 100, find x.  Choose the correct choice from the following options:  A) 3  B) 4  C) 5  D) 6  E) 7

Rationale: "( x + 2 ) × 40 + x × 120 + ( x − 2 ) × 180 / ( x + 2 ) + x + ( x − 2 ) = 100 ⇒ 340 x − 280 / 3 x = 100 ⇒ 40 x = 280 ⇒ x = 7 answer e"
Answer: E