Two balls have the same mass, but one has a larger volume than the other. which ball has the larger density

the ball with the less volume.
To count density you need to divide the mass by the volume. That means larger mass will be more density, but larger volume means lower density. In this case, the ball has the same mass. So the one with less volume has more density.

The charge of an ion with 55 protons and 52 electrons is +3. the reason is because protons are positive, and there are three more than the amount of negative electrons.