Geting exemple? 3 charges loc,
-20are destributed as
Shown in the diagron below
and the resultant force
acting on the 10c charge
go on the loc
charge

Independent variable is something that is changed in a experiment. 

The purpose of a lab is to do your "expirements" the importance of the topic is so you can now what the story is about and the last one is because no one is me with my question ( what is 3 over 4 x - 9 = 27 maybe you can )

Not what goes around on earth but the universe too.