Question

The range of the function f(x) = x + 5 is {7, 9}. What is the function’s domain?

Answer 1

$\bf \begin{cases} \textit{function's range, is the values of "y"}\\ \textit{function's domain, is the values of "x"} \end{cases} \\\\ thus\qquad f(x)=y=x+5\to \begin{cases} y=7\\ y=9 \end{cases} \\\\\\ then\implies \begin{cases} 7=x+5\implies ?=x \\\\ 9=x+5\implies ?=x \end{cases}$

solve for "x"