Three identical metal spheres, A, B and C, stand on insulating stands…

Step 1. A touches B. The total is $8.0\ \mu\text{C} + (-2.0\ \mu\text{C}) = +6.0\ \mu\text{C}$, so each has $+3.00\ \mu\text{C}$. Now A has $3.00\ \mu\text{C}$, B has $3.00\ \mu\text{C}$ and C has $0$.

Step 2. B touches C. The total is $3.00\ \mu\text{C} + 0 = 3.00\ \mu\text{C}$, so each has $+1.50\ \mu\text{C}$. Now A has $3.00\ \mu\text{C}$, B has $1.50\ \mu\text{C}$ and C has $1.50\ \mu\text{C}$.

Step 3. A touches C. The total is $3.00\ \mu\text{C} + 1.50\ \mu\text{C} = 4.50\ \mu\text{C}$, so each has $+2.25\ \mu\text{C}$.