On the number line shown, the tick marks are equally spaced. Which of the lettered points represents $\displaystyle y$?

The answer key says that the correct answer is E, but what I am looking for is an explanation.

Any help as to how to explain the solution to this problem would be much appreciated. I'm trying to help my sister prepare for her SAT.

What I tried was setting $\displaystyle \begin{cases} 2x = x+y \\ 3x = \frac{x+y}{2}\end{cases}$... but that didn't work. In the end, that method resulted in $\displaystyle 3x=\frac{1}{2}(2x) \rightarrow 3x = x \rightarrow x = 1, y = 2$, which is impossible given the graph. I've also tried a number of other things to no avail.

Thanks in advance!