Find the electrical potential energy (EPE) of three point charges placed as follows on the x-axis: +2.0 μC at x = 0, +3.0 μC at x = 20 cm, and +6.0 μC at x = 50 cm. Take the (EPE) to be zero when the charges are far separated.

Answer 1

Hmmm. Total energy?

Putting the first there, no PE.
second one, PE2= kq1q2/distancebetween.

Adding the third one, PE3 adding third is kq3q1/distance13 + kq3q2/distanc12

compute the distances between 1-3, 2-3, 1-2, compute. Then add PE2 and PE3