Answer is 17.
Explanation;
Mean = sum of the value / number of values
To find out the sum of the values you have to add together all given numbers.
Hence,
sum of the values = 12 + 2 + 8 + 6 + 57
= 85
Number of values means number of data that we have.
According to the given data, there are 5 numbers.
Hence,
mean = 85 / 5
= 17