log b​ 8−log b​ 4

The given expression is "log b​ 8−log b​ 4".

This is a subtraction of two logarithms with the same base. According to the properties of logarithms, specifically the quotient rule, the subtraction of two logarithms is equivalent to the logarithm of the quotient of their arguments.

So, we can rewrite the expression as follows:

log_b (8/4)

Simplify the fraction inside the logarithm:

log_b (2)

So, "log b​ 8−log b​ 4" simplifies to "log_b 2".