Question 752609
let speed of boat in still water is x km /h
and speed of current of water  is y km/h
 speed up stream =x-y km/h
  speed of down stream  =x+y km/h
speed =distance / time 
or 
time =distance/ speed
t1=30/x-y
t2 =22/x+y
as per given conditions 
t1 +t2 =8
30/x-y +22/x+y =8 (i)
similarly
40/x-y +44/x+y =12 (ii)
let x-y =u
x+y =v
we can rewrite equation as
30/u +22/v = 8  (iii)
40/u +44/v = 12 (iv)
by solving equations by elimination method 
we can solve  U =5
and V=11
by substitute the value of  u and v 
we can rewrite equations as 
x-y =5
x +y =11
by solving these equations 
we can get 
x=8 km/h
y=3 km/h

ANSWER speed of  boat in still water is 8km/h
and       speed of current of water is 3 km/h