You could just plug in the values into "x" to see which one works out in the inequality:
x = 16
x + 9 < 7 Substitute/plug in 16 for x
16 + 9 < 7
25 < 7 This is not a solution because 25 is not less than 7
x = -6
x + 9 < 7
-6 + 9 < 7
3 < 7 This is a solution because 3 is less than 7
x = 4
x + 9 < 7
4 + 9 < 7
13 < 7 This is not a solution because 13 is not less than 7
x = -2
x + 9 < 7
-2 + 9 < 7
7 < 7 This is not a solution because 7 can not be greater/less than itself
You could have also done this:
x + 9 < 7 Isolate/get the variable "x" by itself in the inequality, subtract 9 on both side
x + 9 - 9 < 7 - 9
x < -2
[x is any value less than -2, so any number less than -2 would be a solution]
