Решение:

-|15 – 3a| = -11

|15 – 3a| = 11

1) 15 – 3a ≥ 0

-3a ≥ -15

a ≤ 5

15 - 3a = 11

-3a = -4

a = 4/3

2) 15 – 3a < 0

3a > 15

a > 5

15 – 3a= -11

-3a = -26

a = 26/3

Ответ: 26/3; 4/3