I'm pretty sure it's density but i need another opinion.

It is density.

The formula of density is p=m/V, where p is the density, m is the mass, and V is the volume.

Therefore, if you're working out mass divided by volume, you're measuring the total amount of mass that can be contained in that volume.

a charge 3q is at the origin, and a charge −2q is on the positive x axis at x=a. part a where on the x-axis would you place a third charge so it would experience no net electric force? enter an expression for the exact answer, which will involve a square-root sign. (do not enter an approximate decimal answer.)

b.

hope this : )