Natalie walked 3/5 mile in 1/2 hour how fast did she walk in miles per hour

Our job here is to convert the given info to the rate (speed) as a unit measurement.  In other words, we need to calculate how fast Natalie walks in 1 hour.

To do this, divide the distance by the elapsed time:

3/5 mile
------------
1/2 hour

This becomes

3
--
5
==   miles/hour
1
--
2

Invert the divisor (1/2) and multiply:

3      2       6
-- * ---  = -----
5      1       5

The correct answer must include units of measurement.  It is

(6/5) mph.