Answer
(a). $x= 1, 4$
(b). $(1, 4)$
Work Step by Step
(a). The solutions of the given equation are the values of $x$ for which $y$ is equal to 4. Therefore, the solutions are the $(y=4)$-intercepts of the graph.
Intercepts of the graph with $(y=4)$ are at $x=1$ and $x=4$
Therefore $x=1$ and $x=4$ are the required solutions.
(b). The solutions of the given inequality are the values of $x$ for which $y$ is more than $4$. Therefore, the solutions are the values of $x$ for which the graph lie $above$ the $y=4$ line.
The given graph lies above $y=4$ line, between $x=1$ and $x=4 $ excluding $1$ and $4$. Therefore required solutions will be open interval $(1, 4)$.