Question

I need help on how to solve this.

x-3>-9

Answer 1

All you do is add the -3 on the x's side of the equation to isolate the variable, just as if the inequality was an equals sign. so:
x>-6

Answer 2

add the -3 over to the -9's side* I should clarify.
You technically add +3 to both sides to cancel -3 on the variable side.