Well it is a simple question. Firstly we should know that the symbol after x means exists in what value?
So, by having a look at the graph we can see that when y or f(x) has the value of -1 at that moment x can take the values ranging from -5 to -3.
SImilarly from the graph we can see that when y or f(x) has the value of 1 at that moment x can take the values ranging from -3 to 1.
Similarly from the graph we can see that when y or f(x) has the value of 4 at that moment x can take the values ranging from 1 to 6.