Question 1170571
The speed of the plane with the wind is 1425 miles/2.5 hours or 610 mph. This speed is the speed of the plane, s, plus the speed of the wind w, or s+w.  Similarly, it is s-w against the wind, and 1425/2.5=570 mph.
These are simultaneous equations.


s+w=610 mph (1525/2.5)
s-w=570 mph
2s=1180
s=590 mph speed in still air.
w=20 mph speed of the wind.