.
=
is your governing equation. It is the direct translation of the condition.
Now solve it for "r", which is the speed of the current.
For this, your first step is to multiply both sides by (24+r)*(24-r).
Good luck !!
If you need more details, read the lessons
- Wind and Current problems
- More problems on upstream and downstream round trips
- Wind and Current problems solvable by quadratic equations
- Unpowered raft floating downstream along a river
- Selected problems from the archive on the boat floating Upstream and Downstream
in this site.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this textbook under the section "Word problems", the topic "Travel and Distance problems".