Hey there!
A variable is an unknown number. It can basically be represented by anything, from a random letter to a shape.
So, the variables in 4a-a=8+a, are a.
To find out the answer to your equation, do these steps:
4a-4=8+a --------Write out the equation.
4a-4+4=8+a+4 -------Equalize both of the sides.
4a=12+a
4a-a=12+a-a
3a=12

=

-----Divide both sides by 3 to simplify it.
Final answer= 4
a=4
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<span>Thank you! :D</span>