In a for loop go over data and sum up all the numbers.

my data is in a data.txt ... (20,10,40,30,60,50,80,100,90,10)

As said, look at the for loop to iterate over the data array. Have a float variable outside of the loop, add all the values of  data to it, and after the loop, divide the value in the variable by the number of items.

And try to find better subjects for your threads, please.

Yeah, in