Question 737098
Watermelon example:
Use rate as watermelons per day and find the rate for 1 person.  


If 13 people pick 112 watermelons in 1 day, 
Then 1 person picks 112 watermelons in {{{1*13=13}}} days.  That is 112 melons per 13 days.


When people work together, their rates are added through simple arithmetic addition.  For n count of people to pick watermelons, the rate will be {{{n*112/13}}} melons per day.


What is wanted?  What is n so that in t=1, the number of watermelons picked is 200.  r*t=Q, where Q is count of melons picked, t is days of picking, and r is rate of the workers picking those melons.
In this situation, {{{highlight((n*112/13)*1=200)}}}, and you want to find n, the number of workers who will pick those 200 melons in that one day.