Question

The mean of a particular set of 7 numbers is 4. Six of the numbers in the set are known: 1,2,2,5,7,and 8.

Identify the missing number.

Answer 1

`(1+2+2+5+7+8+x)/(7)=4\\ (25+x)/(7)=4\\ 25+x=28\\ \boxed{x=3}`