Question

What will happenif you: multiply one charge by 2.0, multiply the other charge by 4.8, and multiply the distance between them by 7.2? 0.18 this is a coulomb's law proportionality question?

Answer 1

Yes it is. 
F1 = k q1 * q2 / r^2
F2 = k *(2*q1) * (4.8 q2) / (7.2 r^2)

Work on F2 for a moment.
F2 = k * 9.6 (q1*q2) / 51.84
F2 = (9.6/ 51.84) *  k * q1 * q2 / r^2
Since k * q1 * q2/r^2 is the same in both questions let kq1*q2/r^2 = m

F1 = m
F2 = 0.18 m

So to make it easier F2/F1 = 0.18m / m
F2/ F1 = 0.18 the m's cancel.

And that should be how you do the question.