Because "plus" has a specific meaning in arithmetic and it is not concatenation.
No it equals 2 10 plus 1 equals 11
Redefine "plus".
10 plus 1 is 11.
12
Unless I'm misunderstanding the question, 1 plus 1 plus 1 equals 3 CAN be written as a multiplication sentence: 1 times 3 equals 3.
A= 2
11
x=-11
If: 5a-1+a = 11 Then: a = 2
(11, 1, 0) and (0, 1, 11) are the two possible solutions.
-10
73