$(-\infty, 5)$ Refer to the image below for the graph.
Work Step by Step
Graph each inequality. (refer to the attached image below) The conjunction used is OR, which means that the solution set contains the combined elements of the two inequalities. $x \lt 4$ includes all the numbers to the left of $4$. $x \lt 5$ includes all the numbers to the left of $5$. Combining the elements of these two inequality gives the solution set; $(-\infty, 5)$