Answer:
Step-by-step explanation:
Let the speed of the plane in still air and speed of wind are Â
P  and  W  km per hour.
The speed of the plane with wind is Â
P+W=189 km per hour  ______________ (1)   Â
The speed of the plane against wind is
P-W=155 km per hour __________________ Â (2)
Now Adding equations (1) and (2) Â we get
 P+W=189
[tex]P-W=155[/tex]
______________
[tex]2P=344[/tex]
[tex]P=\frac{344}{2}[/tex]
Substituting the values of P in the equation (1) we get Â
[tex]172+W=189[/tex]
[tex]W=189-172[/tex]
[tex]W=17[/tex]