5y- 1=3x+5…②

Solution: Obtain from ①.

y=3x-5…③

Substitute ③ into ② to get.

5(3x-5)- 1=3x+5

15x-25- 1=3x+5

15x-3x=5+25+ 1

12x=3 1

X= 3 1/ 12

Substitute x= 12/3 1 into ①.

y= 1 1/4

(2)?

2. solution: let the average speed be xkm/h and the wind speed be ykm/h.

(X+Y)*5/2= 1200

(X-Y)* 10/3= 1200

Equation 1 is transformed into X=480-Y generation equation 2 by method of substitution, and the solution is: Y=60, Y=60 generation original equation? X=420

So the average speed of the plane is 420KM/H and the wind speed is 60 km/h.