Coulomb’s Law between three charges on the same axis (YF 21.19)

Three point charges are arranged along the x-axis. Charge q1 = +3.00μC is at the origin, and charge q2 = -5.00μC is at x=0.200m. Charge q3 = -8.00μC.
Where is q3 located if the net force on q1 is 7.00 N in the -x direction?

 

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