Answer:
[tex]\frac{63}{15 - c} - \frac{63}{15 + c} = 4[/tex]
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
[tex]\frac{63}{15 - c} - \frac{63}{15 + c} = 4[/tex]
