Question 519897
speed of container ship = x mph
in 4 hours it travels 4x

aircraft carrier speed = 30 mph

catchup speed = 30-x

time taken = 8 hours

d/r=t

4x/(30-x)=8

4x=8*30-8x
4x=240-8x
12x= 240 mph
x=20 mph speed of container ship