Is my work correct?
\(1. \quad |F_E|=k|\frac{q_1q_2}{r^2}|\\|\frac{F_E}{k}|=|\frac{q_1q_2}{r^2}|\\\frac{F_E}{k}=\frac{q_1q_2}{r^2}\\ q_1=\frac{(F_E)(r^2)}{kq_2}\\ Correct.\)
2nd question. Too lazy to type in LaTeX. Correct.
3rd question Correct.