Question 1013599
Coulomb's Law applies here:
{{{F = kq[1]q[2]/d^2}}}
Here the charges are identical, call them q and solve giving us
{{{q^2 = (Fd^2)/k = (.3)(.75^2)/(8.99 * 10^9) = 1.877 * 10^-11}}}
and
q = 4.33 x 10^-6 C