According to the meaning of the question: 5/2 (x+y) = 1200 ①
10/3(X-Y)= 1200 ②
Complete the equation: 3X+3Y= 1400 ③.
4X-4Y= 1440 ④
From ③: X=480-Y ⑤
Substitute ⑤ into ⑤ to get:
4(480-Y)-4Y= 1440
1920-4Y-4Y= 1440
1920- 1440=8Y
480=8Y
60=Y ⑥
Substituting 6 into 3 gives:
3X+3×60= 1440
3X= 1440- 180
X= 1260÷3
X=420
A: The average speed of the plane is 420 kilometers and the wind speed is 60 kilometers.
PS: I have some difficulty in writing math. You can also use addition and subtraction.