We know, force is given by :
[tex]F=\dfrac{kq_1q_2}{r^2}[/tex]
Here, k in a constant.
[tex]Net \ Force = F_1+F_2\\\\Net \ Force = k(\dfrac{Qq_1}{r_1^2}+\dfrac{Qq_2}{r_2^2})\\\\Net \ Force = k( \dfrac{-3}{50}+\dfrac{2}{50})\\\\Net \ Force = 9\times 10^9\times \dfrac{-1}{50}\ N\\\\Net\ Force = -1.8\times 10^8\ N[/tex]
Hence, this is the required solution.