Three times a number is 3n. Nine less than that is 3n-9. This is NOT the same thing: 9-3n. Subtraction is not commutative. If n was 1, for example, 3(1)-9=-6. Looking at the other expression, 9-3(1)=6. 6 and -6 are definitely not the same number. So be careful how you set up your expression. Our inequality then would be [tex]3n-9\ \textgreater \ 40[/tex]
