13) lg 16-lg(4x - 8) = lg 5;

13) lg 16 - lg(4x - 8) = lg 5

Используем свойство логарифмов: log_a b - log_a c = log_a (b/c)

lg(16 / (4x - 8)) = lg 5

16 / (4x - 8) = 5

16 = 5(4x - 8)

16 = 20x - 40

20x = 56

x = 56/20 = 2.8

Проверка:

lg 16 - lg(4*2.8 - 8) = lg 5

lg 16 - lg(11.2 - 8) = lg 5

lg 16 - lg(3.2) = lg 5

lg (16 / 3.2) = lg 5

lg 5 = lg 5

Ответ: x = 2.8