How to move vertices by the straight line?

Hi!

Sorry for noob question, I can’t do this easy transition.
Please, help to understand, how to solve it?

In this case it could be simpler to just add a straight cut using the knife tool and then delete unneeded faces. You can do that on one side and then use Symmetrize to make the model symmetrical again.

Otherwise, you could try the Shear tool: select the three vertices you have circled on the right side, change pivot point to ‘3D Cursor’ (since you already have it conveniently placed), and Shear. Then, once again Symmetrize to bring the edits to the other side.

Welcome to BA!

Big thanks! I forgot about knife tool. :wink: