Algebraic quantity that may work to contain two bits of arithmetic (8)
I believe the answer is:
variable
'algebraic quantity' is the definition.
'variable' can be an answer for 'quantity' (variable quantity is a kind of quantity). I'm not sure about the 'algebraic' bit.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for variable that I've seen before include "Not steady or regular" , "Prone to change" , "Changeable or inconstant" , "Mutable" , "Unsteady" .)