an obtuse angle is an angle with more than 90 degrees and less than 180. so, we can add < 180 and > 90 to the expression, making it the inequality 180 < 3x + 24 > 90. we then solve.
3x + 24 > 90 and 3x + 24 < 180
3x > 66 and 3x < 156
x > 22 and x < 52
so x can be anything more than 22 and less than 52 (it cannot be 52 or more or 22 or less)
hope this helps!