Since J and N can do the job inhours, their combined rate of work is . It means that they can do of the entire job in one hour, working together. Jenny's individual rate of work is of the job per hour. Hence, Natalie's individual rate of work is this difference - = = = = of the job per hour. It means that Natalie can do the entire job in 6 hours, working alone. ANSWER
Let time Natalie takes, alone, be N Then Natalie can doof job in 1 hour Since Jenny takes 7 hours alone, Jenny can do of job in 1 hour With both completing the job in , we get the following: 42 + 6N = 13N ------ Multiplying by LCD, 42N 42 = 7N Time Natalie takes, alone, or