Two sailors sail against the current for 200 miles from Belgrade to Budapest and then sail with the current on their return journey. In total, they sailed for 20 hours and their yacht traveled 15 mph in still water. What is the speed of the current in the river?

current rate =  c =  5* mph  =  8.66 mph

Step-by-step explanation:

it looks like we do not know 2 things

the rate against the current and the rate with the current.

let  c = rate of current

  15 mph = rate of the two sailors.

15 + c = rate with current

c - 15 = rate against current

total time travel = 20 hours

(15 + c)*a  = 200

(15 - c)*b = 200

a + b = 20

b = 20 - a

Let us read this right,  I think the total trip is 400 miles

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(15 - c)*(20 - a) + (15 + c)*a = 400

300 - 20c -15a + ac + 15a + ac = 400

300 - 20c + 2ac = 400

100 = -20c + 2ac

50 = 10c - ac

50 = c*(a - 10)

c = 50/(a - 10)

assuming   (15 + c)*a = (15 - c)*b

(15 + c)*a = (15 - c)*(20 - a)

15a + ac =  300 + ac - 20c - 15a

30a = 300 + 20c

a = 10 + (2/3)c

c = (3/2)*(a - 10)

(3/2)*(a - 10) = c = 50/(a - 10)

(a - 10)^2 = 100/3

a = 10  + root(100/3)

b = 20 - a  = 10 - root(100/3)

c = 50/(a - 10) =  50 / (10 + root(100/3) - 10)  =  50/ root(100/3)

c = 50 / (  10/  root(3)) =  5  root(3) =

75%

step-by-step explanation: