Their sum is 100N/C since they are repulsive , No idea about direction XD
See if you can find a picture of the electric field surrounding a positive charge, and for a negative charge (your text or the web should have this). What direction are the arrows representing the fields directed in each case?
No directions are shown !
That's just the problem statement. You're expected to know the directions to assign to the fields produced by positive and negative charges. See if you can find another image showing the fields surrounding charges. I found several in a few seconds by googling "electric field".
ahh i thought you were meaning from the question itself ... XD
Okay! So now you can assign a direction to the sum of the fields that you calculated earlier, right?
well , this is the point im not getting and need help
Respecting to P , the direction to right is positive , so E2 - E1 - E3 = 0 ,,, that means E3=E2-E1 which results into 100N/C ...
Yes, that's the idea. You set up coordinate axes and determine both the magnitude and directions of the fields due to each charge before you start adding or subtracting them as the situation warrants. You will find that the same concept applies even if the charges are not along a straight line, in which case you'll deal will all the components of the vectors (time to review your trigonometry!).
