Answer:
4.5 miles per hour is her rate in miles per hour 
Explanation:
We want to convert 20 ft per second to miles per hour
If she jogs 20 ft in 3 seconds , then in one second , she will jog 20/3 ft 
So convert 20/3 ft/second to miles per hour 
Mathematically;
1 mile = 5280 feet 
So one feet = 1/5280 mile 
1 hour = 3600 seconds 
1 second = 1/3600 hour 
So, to go from miles/hour to ft/second ; we shall multiply by 1/5280 and divide by 1/3600
Hence; we have;
(20/3 * 1/5280)/1/3600
= 20/3 * 1/5280 * 3600/1
= 4.4545 which is 4.5 miles per hour