Can I safely use a 9w LED bulb in place of a 40w incandescent?
Yes.  The fixture is concerned with heat.  Your LED light bulb makes about 9 watts of heat.   Your fixture is rated for a bulb that makes 40 watts of heat.

With an incandescent bulb, 98-99% of its wattage turns directly into heat.  Even LEDs, 90% of their wattage turns into heat. For thermal planning, it's not worth pulling out the calculator. You're "close enough" just pretending it all becomes heat. 

On the LED bulb, when it says "75 watt equivalent" it's trying to give ordinary consumers a general sense of how bright the bulb is - i.e. about as bright as an old style 75 watt incandescent.  The more proper way to say that is "950 lumens", which is a unit of measure for describing brightness to human eyes.