Question about Coulomb's law
First of all, I would like to bring up the points that others have brought up, We cannot solve all of the question for you. You have to show some signs of trial and we will guide you from there on.   With that being said, you have mentioned that you know how to find one of the variables from the equation: $$F={kq_1q_2\over r^2}$$ Now this equation on its own is not enough to solve this question as it enquires about electric field. I think you should read some about electric field wikipedia Now for the starters the relation between electric field and Force is given by: $$F=qE$$

Also the electric field follows the principle of superposition Wikipedia
that is the resultant Electric field is the addition of electric field produced by all charges. Electric field also is a vector. Now using the above you can find the electric field at point X  To find the equilibrium you just have to find the point in the electric field which experiences the same amount of force from both the directions. 

PS : I think this question should be asked in the Physics stackexchange