Problem Solving with Quadratics

Can any1 help me with these problems - i cant see to work them out :S

1. Find the width of a uniform concrete path placed around a 30m by 40m rectangular lawn given that the concrete has area on quarter of the lawn?

2. If the average speed of an aeroplane had been 120kmph less, it would have taken a half an hour longer to fly 1000km. Find the speed of the plane?

3. A group of elderly citizens hire a bus for $160. At the last minute 8 of them miss the trip due to illness. Therefore the other citizens had to pay an extra $1 each - how many elderly citizens went on the trip?

Thanks, much appreciated