To simplify the expression "14m - 17m - 9m" when m is equal to 30, you can substitute the value of m into the expression and then perform the calculations:
14m - 17m - 9m = (14 * 30) - (17 * 30) - (9 * 30)
= 420 - 510 - 270
= (-90)
So, when m is equal to 30, the simplified expression is -90.