Question 694675
Plane  	speed	x	km/h									
wind   	speed	20	km/h									
..												
against currentspeed	x-	20										
withcurrent 	x+	20										
..												
Against current		5	hours									
with current x+y		4	hours									
Distance is same.  D=r*t												
5	(	x	-	20	)	=	4	(	x	+	20	)
5	x	-	100			=	4	x	+	80		
5	x	-	4	x	=		100	+	80			
1	x				=		180					
/	1											
x				=		180	km/h					
Plane  	speed	=	180	km/h