The graph of the function f(x) = (x – 4)(x + 1) is shown below. Which statement about the function is true?

So, at the beginning there are a total of 25*3=75 siblings (we can assume that each of them had exactly 3 siblings, that's what average means; that we can assume this).

Now we have 25+1=26 students and the number of siblings is 75+8=83

and the average is, and rounded it's 3.19.