If Tim can swim 50 meters in 60 sec. But he slows down 12 sec the remaining race. How long does it take Tim to swim a 400 meter race.

I'm not quite sure what you are asking, but I will do my best to answer you.

I am assuming that "slows down 12 sec the remaining race" means that each 50m was 12 seconds slower than the original 50m.

There are eight 50m in 400m, with the first 50m completed in 60 seconds and the remaining 7 units of 50m done in 72 seconds each.

I'll let you do the calculations. I hope this helps. Thanks for asking.