2. In the equation, some letters represent unknowns (variables), some letters can be regarded as constants, and the algebraic expression of unknowns with letters as constants can also be understood as the values of unknowns (variables), such as x = a-2by = 2a+b;

3. In inequality, value is the range of values of variables.

So the understanding of "value" depends on the specific topic environment. If summed up in one sentence, it is the "result" of the variable required by the topic.