Question

The force in the middle of two identical charges separated by 1.77 cm is equal to 70N. What is the magnitude of the two forces? 

Answer 1

The Coulomb's law says

$$F=k\frac{|q_1||q_2|}{r^2}$$

The magnitude of charges

$$q=\sqrt{\frac{Fr^2}{k}}=\sqrt{\frac{70*0.0177}{9*10^9}}=1.17*10^{-5}\:\rm C$$