Two identical bodies, the charges of which are 5 µC and –15 µC. brought into contact. What were the charges of these bodies after that?

When charged bodies come into contact, charge distribution occurs. From a body with a large charge, part of the charge passes to another body, trying to divide the total charge of a closed system of bodies exactly in half.
q1 = 5μC = 5 * (10 ^ (- 6)) C
q1 = -15μC = -15 * (10 ^ (- 6)) Cl
We use the formula
q1 * = q2 * = (q1 + q2) / 2
q1 * = q2 * = (5 * (10 ^ (- 6)) + (- 15 * (10 ^ (- 6)))) / 2 = (- 10 * (10 ^ (- 6))) / 2 = -5 * (10 ^ (- 6)) Cl = -5μC
q1 *, q2 * charges of bodies after contact
so as not to get lost with parentheses
q1 * = q2 * = (5mk + (- 15mk)) / 2 = (- 10mk) / 2 = -5mkC