Classic puzzles in two variables

Question

A summer begins a trip Upstream. He sends a total of 3 miles in 2.5 hours. He then turns around and swims with the current to his original starting position. It's the return trip takes him only 0.3 hours, how fast is the current how fast does he swim when there is no current?

Answer 1

x=his speed

y=current's speed

 

x-y= 3/2.5=1.2

x+y= 3/0.3=10

2x=11.2

x=11.2/2= 5.6 mph

y=10-5.6= 4.4 mph