How would u do this? i needz . plz

Kelli swam upstream for some distance in a hour. she then swam downstream the same river for the same distance in only 6 minutes. if the river flows at 5km/hr, how fast can kelli swim in still water?

Would love some on this! include step by step have a good day!

Betty correctly answers 30 questions on your math test there are 40 questions on the test what percent of the questions did she answered incorrectly