Given,
The total charge of the particle, Q=+24e
The charges of each of the 3 particles, q=2e.
In order for the equation of the decay to be balanced, the total charge before and after the decay must be equal.
Therefore,
Where Qc is the collective charge of the remaining 9 particles.
On rearranging the above equation,
On substituting the known values in the above equation,
Therefore the collective charge of the rest of the particles is 18e