What is Roman Leeter X?

First of all, to correct your English spelling.

It is 'letter' , NOT 'leeter'.

To answer you question

X = 10

Here is the table of Roman Numerals

I. = 1

V = 5,

X = 10

L = 50

C = 100

D = 500

,M. = 1000

The current year '2026' is ' MMXXVI'.