So basically, you have T, O, and Y.
We know that O is somewhere between T and Y. You can check the image if you're having trouble.
Now, we subtract the distance between T and O to get their distance between each other.
Since we know that the distance between T and Y is 13, we subtract 5 from 13, and we get 8.
Now that we know that the distance between O and Y is 8, we will add this value to the coordinate of O, which is -2.
The coordinate of Y is 6.
I hope that answers your question. (Sorry for taking a long time, I was called.)
If you're still having trouble, don't hesitate to message me.