Question

−1 < 9 + x < 17
$−1 \ \textless \ 9 + x \ \textless \ 17$

Answer 1

divide the equation in two ways to solve the solution;
The first solution:
$- 1 < 9 + x \\ - 1 - 9 < x \\ - 10 < x \\ x > - 10$
another solution:
$9 + x < 17 \\ x < 17 - 9 \\ x < 8$
Therefore,
$- 10 < x < 8$