it would be more helpful with clear steps thanks

1) In the figure, charge q1 = -17.1 x 10-6 C is placed at the origin and charge q2 = 4.2 x 10-6 C is placed on the x-axis, atx = -0.20 m. Where along the x-axis can a third charge O = -6 uC be placed such that the resultant force on this third charge is zero? 0.20 m