The average of 6 observations is 12. A new observation is included and the new average is decreased by 1. The seventh observation is? Choose the correct choice from the following answers
A) 1  B) 3  C) 5  D) 6  E) 7

Rationale: "let seventh observation = x . then , according to the question we have = > ( 72 + x ) / 7 = 11 = > x = 5 . hence , the seventh observation is 5 . answer : c"
Answer: C