Question

A positive charge, q1, of 5 µC is 3 × 10–2 m west of a positive charge, q2, of 2 µC. What is the magnitude and direction of the electrical force, Fe, applied by q1 on q2?

Answer 1

The law you need is :
lets call the constant c = 4pi*epsilon naught*r2.
where r is radius ( or seperation of the charges). epsilon naught is a constant of about 8.85*10^-12 or something like that. and 4 pi is just 4 times pi.
the actual equation is 
FORCE= (q1*q2)/c