ANSWER
All real numbers
EXPLANATION
To solve this inequality, first, divide both sides by 3,
[tex]\begin{gathered} \frac{3\left(5x-4\right)}{3}\lt\frac{15x}{3} \\ \\ 5x-4\lt5x \end{gathered}[/tex]
Then, subtract 5x from both sides of the inequality,
[tex]\begin{gathered} 5x-5x-4\lt5x-5x \\ \\ -4\lt0 \end{gathered}[/tex]
-4 indeed is less than 0, and this is valid for any value of x in the real numbers - i.e. any real number for x satisfies the inequality.
Hence, the solution is all real numbers.
