"Below is an ”oracle” function. An oracle function is
a function presented interactively. When you type in an x value,
and press the –f–> button and the value f (x) appears in the right
Do you not understand what this says? On the webpage you are working on, by typing a value of x into the blank and pressing the "f->" button you see the value f(x). Since the copy you made does not have that button, no one here can see what values you are working with. To find the limit as x goes to .6666 (2/3), you will have to put in values of f very close to .6666 and see what value you get.