By definition, a function is a relation in which each input value (x-value) has one and only one output value (y-value).
In this case, you need to find all input values for the following output value:
Knowing that the output values are the y-values, you can rewrite it as:
Then, you can find the points with -5 as their y-coordinate. For the blue graph, you get:
For the red function, you can draw a horizontal line. See below:
Notice that the x-coordinate of the point whose y-coordinate is -5, is between -3 and -4, so you can set up that:
Therefore, the answers are: