I can not decide on the correct choice of the simple or installable trigger?

Question

Google Apps Script

To clarify my problem, I will make a conditional task, so it will be clearer what the question is all the same, since I am just a beginner.
There is a table of the Owner in which, through the function after entering X , the equation X * 5 = Y is solved (everything in the table is protected except X )
So X must be entered by users and the table shows the answer in the form of Y value
The user can only edit X and he must see result Y after editing (entering) X

Ownershould capture all users and their entered X values .
User1 entered 5 received 25
User2 entered 100 received 500 Essence of the question: by selecting the onEdit() trigger, we can identify the user (Session.getEffectiveUser();), we can store the value of X , but we cannot show him the result of Y . Since the function will work from the user and will not allow the function to write a value to Y . By choosing an installable trigger, we can show the user the result Y




, but we won't be able to determine the user itself via (Session.getEffectiveUser();).

How to make it so that would determine who contributed X and show the answer Y in the table.