How do you defeat a level 9 NPC on Evony with few losses?

You really should not attack a lvl9 npc as a level 10 has about the same losses and more resources. In doing so, I would send 1k transporters, 2k warriors, 2k workers, 1.5k scout, rest archers (93.5k). If you have a hero at lvl 70 or so, your losses should be about 7k archers and the other troops (minus transporters).

If you are attacking to take the city, replace transporters with archers. This wave will take out the troops, but you will want to have continuous waves following up every 30-45 seconds. These are called loyalty waves. The first loyalty wave should be large (maybe 40k archer/40k warrior) The rest of the loyalty waves should be about 20k archer/20k warrior mix. In order to have this kind of timing, you want to have your city about 1-2 miles away and be able to launch attacks with 9-10 heroes (Feasting Hall lvl 10).