By definition, the function is a relation in which each input value (x-value) has one and only one output value (y-value).
In this case, you have the following function:
[tex]g\mleft(x\mright)=x-11[/tex]And you need to find the input value that has the following output value:
[tex]g\mleft(x\mright)=-7[/tex]In order to find that value of "x", you need to substitute the given ouput value into the function:
[tex]\begin{gathered} g\mleft(x\mright)=x-11 \\ -7=x-11 \end{gathered}[/tex]And now you must solve for the variable "x". To do it, you must apply the Addition property of equality by adding 11 to both sides of the equation:
[tex]\begin{gathered} -7+(11)=x-11+(11) \\ x=4 \end{gathered}[/tex]The answer is:
[tex]x=4[/tex]