ОДЗ:
x+4 > 0
x > -4
x-11 > 0
x > 11
log2(x+4)-log2(x-11) = 4
log2((x+4) / (x-11)) = 4
2^4 = (x+4) / (x-11)
16(x-11) = x+4
16x -176 = x+4
16x -x = 4 + 176
15x = 180
x = 12, 12 > 11
Проверка:
log2(12+4)-log2(12-11) = 4
log2(16)-log2(1) = 4
4 - 0 = 4
4 = 4
Ответ: 12.