the average of 6 observations is 12 . a new observation is included and the new average is decreased by 1 . the seventh observation is ?
"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"
subtract(multiply(subtract(12, 1), add(6, 1)), multiply(12, 6))