The answer is C
Please mark as a brainliest above my comment
Answer:

Step-by-step explanation:
The systems of equations are
Let us assume the rate of the current be c
Now actual speed against the current is (15 - c)
And, the actual speed with the current is (15 + c)
Here we applied the time formula i.e. distance by speed
Also the upstream time - downstream time = 4
Now the equations are

(X+4)(X-4) is the LCD because you just have to look at the denominators and see what factors or values are not already part of your LCD.
Answer:
15/40
Step-by-step explanation:
