Question

In a function table, which isn't supposed to have more than one of the same, y or x when y is a function of x

Answer 1

The x-values. For y to be a function of x, each x (input) can have only one y (output). You can repeat y-values, but if the same x appears with two different y's (e.g. (1,2) and (1,3)) then it is not a function. (If the same x repeats with the same y it's technically still a function but redundant.)