1. The route from city a to city B is 1200 km long. It takes 2 hours and 30 minutes for an aircraft to fly from city a downwind to city B, and 3 hours and 20 minutes to fly from city B upwind to city A? 2. A unit marches for 4 hours on the first day and 5 hours on the second day, with a total of 98km on the two days, and 2km less on the first day than on the second day. What is the average speed of March on the first day and the second day? 3. Each tin sheet can be used to make 25 tins or 40 bottom tins. One tin body and two bottom tins form a tin. Now there are 36 tins. How many tin bodies and bottom tins can make the body and bottom of the tin just match?

1. The route from city a to city B is 1200 km long. It takes 2 hours and 30 minutes for an aircraft to fly from city a downwind to city B, and 3 hours and 20 minutes to fly from city B upwind to city A? 2. A unit marches for 4 hours on the first day and 5 hours on the second day, with a total of 98km on the two days, and 2km less on the first day than on the second day. What is the average speed of March on the first day and the second day? 3. Each tin sheet can be used to make 25 tins or 40 bottom tins. One tin body and two bottom tins form a tin. Now there are 36 tins. How many tin bodies and bottom tins can make the body and bottom of the tin just match?

1: Let the average speed of the aircraft be x and the wind speed be y, and the equations are established
(x+y)2.5=1200,(x-y)(10/3)=1200,x=420km/h,y=60km/h
2: Suppose that the speed of the first day is XKM / h, and that of the second day is YKM / h,
4x+5y=98,5y-4x=2,x=12km/h,y=10km/h
3: There are x cartons on the body and Y cartons on the bottom,
x+y=36,25*2x=40y,x=16,y=20