1(: if the variable is not given to you
There are many expressions that have this value. The simplest one is the number zero itself.
When two expressions are equal to each other they form an equation.
they are expressions
No single number can be negative or positive. There are equations or expressions whose value can be either but not a number.
None of "these" expressions represent anything!
Absolute value is a number's distance from zero on the number line.