If the length is X
X+X+X = 9X+6
3X=9X+6
-6X=6
X=-1
but because length can't be negative X=1
You use a closed dot with the greater than or less than with the line under the symbol or the greater than or equal to or the less than or equal to symbols. The line indicates a closed dot.
The set is not closed
Example
-4 * -2 = 8
8 is not a negative integer
-20%
work:
(24-30):30*100=
(24:30-1)*100=
80-100=-20
