Answer:
0.86 m
Step-by-step explanation:
q₁ = magnitude of positive charge = 5 x 10⁻⁶ C
q₂ = magnitude of negative charge = 3 x 10⁻⁶ C
r = distance between the two charges = 0.250 m
d = distance of the location of third charge from negative charge
q = magnitude of charge on third charge
Using equilibrium of electric force on third charge



d = 0.86 m