Answer: 3 kilometers per hour
Step-by-step explanation: Jill walks 1.5 kph and they meet in 2 hours so she walks 3 kilometers total, but since there's 9 kilometer distance and she covered 3 then joe covered the other 6 kilometers. So it takes joe 2 hours to walk 6 kilometers, and divided into 1 hour is 3 kilometers. So joe walks 3 kilometers per hour.