Q is the set of the rational numbers
Rational numbers are all numbers that can be put in the form of a/, where b is not equal to zero.
Examples:

The given equation is

Insert log on both sides

Use the rule of power with a log

Divide both sides by log(1/5)

Since we can not put the value of x in the form of a/b, then
The equation has NO solution in Q (or empty set { } or Nul)