Charges a and b in the figure are equal. each charge exerts a force on the other of magnitude
f. suppose the charge of b is increased by a factor of 4, but everything else is unchanged.

The formula used to determine the force between two charges is
F = kQ1Q2/d2
The first has a and b with equal charges
F = k q q /d2
F = kq2/d2
In the second scenario, the charge of b is increased by 4
F = k q 4q /d2
F = 4kq2/d2
This means that increasing the charge by 4 also increases the force between  them by 4.

The purpose of a lab is to do your "expirements" the importance of the topic is so you can now what the story is about and the last one is because no one is me with my question ( what is 3 over 4 x - 9 = 27 maybe you can )