Answer:
217
Explanation:
The mean or average is calculated by taking the sum or addition of the data points, and dividing by the number of data points. This is known as a sample of data because it is a subset of data.
In simple terms, add all the numbers up, and divide by the number of numbers.
Arithmetic mean of a sample:

In this case the mean or average is:
Mean = 284 + 192 + 264 + 128 / 4 = 868 / 4 = 217