@Melody I'm sorry for interupting. I will go back to Brainly, where I posted questions before, and never felt so shameful. I have used it for 2 years already.
@ilorty I will answer it. https://www.geogebra.org/calculator
This is my graph. You have to plot the points.
So, X=(-1-2,-7-14) which is (-3,-21). So, -24.
I also don't think you can see the graph. Sorry. I'll show another way.
XZ=ZY and XZ+ZY=XY, which means X,Y, and Z form a degenerate triangle. (I don't know if you have learned it yet. Sorry if you haven't.) Since from Y to Z, we go 2 steps left and 14 steps down, we do the same to arrive at X=(-1-2,-7-14) which is (-3,-21). So, X=-24. I hope you understood. I am very sorry for the damage I have made on this website. I will not use it again, so I will not break your rules.
Thank you! I was just confused on what you meant by adding points. Now I see. I have learned lots from your answer :)
P.S. Do not be ashamed of yourself! Everybody makes mistakes! All you have to do is learn from them, and you will live a happy life