Well, that depends.
1. Are you learning to fly in the US?
2. If so then you need 40 hours total. 20 with an instructor and 10 solo. Yes, that makes 30 hours. the other 10 are of your instructors choosing. Could be solo or dual.
3. Most of my students took 50 hours plus.
4. If you only fly once a week, expect weather cancelations to fill some time.
5. Some people don't learn as fast as others. If you are older expect it to take longer.
6. Enjoy the journey getting your license, you will learn alot along the way.
If you have more questions, please ask as there are alot of knowledgable folks on this site!