(21:22:11 on the 22nd) Ship a flows downstream from wharf a, and ship B flows upstream from wharf B. the two ships are traveling at the same time and meet at the midpoint. The speed of ship B downstream is twice that of ship a upstream. The known water speed is 4km / h. how to calculate the speed of the two ships in still water?

(21:22:11 on the 22nd) Ship a flows downstream from wharf a, and ship B flows upstream from wharf B. the two ships are traveling at the same time and meet at the midpoint. The speed of ship B downstream is twice that of ship a upstream. The known water speed is 4km / h. how to calculate the speed of the two ships in still water?

Let the velocities of a and B be x and Y respectively
The equation is as follows
X + 4 = y-4
y+4=2*(x-4)
The solution of the equation is: x = 20, y = 28

21/5×(22/7-22/3)×(-5/22)

21/5×(22/7-22/3)×(-5/22)
=21/5×(-5/22)×(22/7-22/3)
=-21/22×(22/7-22/3)
=-21/22×22/7-22/3×（-21/22）
=-3-（-7）
=-3+7
=4