It equals 8 1/8 because 5 + 3 = 8 plus the 1/8
To find the mean you first add all the numbers up you get each day
12+16+0+8+31+28+17=112
Than you divided it by how many days there are...
112/7=16
So the mean is 16
As they are written, they are all linear. I think you meant for the third one to be y=x^2. if that is true then y=x^2 is a quadratic and therefore is the answer