The average of a set of 20 numbers is P. If one of the numbers from the set is replaced with 58, then the average becomes (P - 2). What is the value of the number that is replaced?

98

According to question ,

Sum of 20 numbers = 20P

New sum of 20 numbers = 20( P - 2 ) = 20P - 40

Sum decreased by 40 . So , Replaced number is 58 + 40 = 98