The 3rd charge could end up anywhere on the line, left, right or between the first 2 charges. What is the equation for the electric field E generated by a charge at some distance...?
Yes, that is correct. It's good that you see that.For Force its, F = KQQ/r2
The way I understand the problem is it could either be on the left or right of those two charges. Because if it was in the middle, the third charge will experience a net force directed to the right. Right?