参考答案：20 years

解析：[听力原文] 5-8
W: Welcome to our programme. Today we have invited Fred Wocson, a driving instructor of over 20 years experience to talk to us about learning to drive. Well, Fred, do you think it’s getting expensive to learn to drive these days
M: Well, it depends. If you come for a private instructor like me, it’s going to be a bit less expensive than going to a big school. The thing is, people have usually heard of the big school and trust them. Well, I get customers through personal connections.
W: Does that mean you have to try hard to get customers
M: Not now, when I started I had to. But at the moment I am fully booked and my prices are quite competitive.
W: Learning to drive is usually a nervous experience for beginners. What do you think
M: Well, it can be. But I try to get them to sit quietly in the drive’s seat for a few minutes. With their eyes closed, you will be surprised how it changed some people. They fell much more ready for drive if they had a few quiet moments.
W: Yes, I suppose some people are much more nervous than others.