Write an example of an algebraic expression that always has the same value regardless of the value of the variable.

An algebraic expression that always has the same value regardless of the value of the variable is called an identity. An identity, in mathematics, is a relation between A and B that would result to an equality of the two. It should be expressed as A = B wherein both values has some variables that would produce the same value no matter what will be the values used for the two functions. An example would be 

5(2x+3)=9x+15+x

Assuming x would be 1, when we simplify the equation above, both sides would have the same value of 25. 

5(2(1)+3)=9(1)+15+1

25 = 25

The answer would be 24mm