“Why didn’t the Romans find algebra very difficult?”/“Because X was always 10.”

An algebra riddle has been printed on many images:
 
Q: Why didn’t the Romans find algebra very difficult?
A: Because X was always 10.
   
“The Romans didn’t find algebra very challenging, because X was always 10” was posted on the newsgroup alt.society.zeitgeist on June 20, 2000.
 
         
Google Groups: alt.society.zeitgeist
Math gets complicated
Twodobes
6/20/00
The Romans didn’t find algebra very challenging, because X was always 10.
 
Google Groups: alt.support.single-parents
Reese still can’t admit his mistakes…
The Stare
2/28/01
(...)
The Romans didn’t find algebra very challenging, because X was always 10.
   
Google Groups: alt.humor.puns
Puns of the Weak 03-01-04
Stan Kegel
3/1/04
(...)
The Romans didn’t find algebra very challenging, because X was always 10.
(Aaron Dragushan)
 
Twitter
Invest Entrepreneur
@investrepreneur
The Romans didn’t find algebra very challenging, because X was always 10.
12:50 AM - 5 Mar 2009
   
Twitter
Michael Klobe
@klobetime
Algebra was easy for the Romans because “X” was always 10.
3:06 PM - 11 Mar 2009
   
Google Books
Change and Invariance:
A Textbook on Algebraic Insight into Numbers and Shapes
By Ilya Sinitsky
Boston, MA: Sense Publishers
2016
Pg. 226:
A joke: The Romans didn’t find algebra very challenging, because X was always 10.
   
Reddit—Jokes
Why didn’t the Romans find algebra very challenging?
submitted May 17, 2016 by Dodgerballs
Because X was always 10
 
Reddit—Jokes
Why didn’t the Romans find algebra very difficult?
submitted April 10, 2018 by Mikluvinb
Because X was always 10