question: How many population of people of 25 to 64 and over 65 years combined?
#1 return people 
#2 return #1 that are from  25 to 64 years 
#3 return #1 that are over 65 years 
#4 return number of  #2 
#5 return number of  #3 
#6 return the  sum of #4 and  #5