how much work is done in bringing three electrons , which are intially a great disance apart to how fats will it be moving then it is at distance ?
Your question does not make sense as written. How closely are the three electrons brought together? What is the "it" you are referring to?
"How fats" is not a location. Neither is "How fast"
If "a" is the separation of the electrons in an equilateral triangle configuration,
Bringing in the first electron requires no work.
Bringing in the second electron requires k^e^2/a
Bringing in the third electron requires
2ke^2/a
The total work required is
3 k e^2/a
k is the Coulomb constant