13. Ana and Beth do a job together in three hours. Working alone, Ana does the job in 5 hours. How long will it take Beth to do the job alone? a. 3 and 1/3 hours b. 2 and 1/3 hours c. 3 hours d. 7 and 1/2 hours

 d. 7 and 1/2 hours

Step-by-step explanation:

Given : The time taken by Ana and Beth do a job together = 3 hours

Time taken by Ana to do a job alone = 5 hours

Let t be the time taken by Beth to do a job .

Then, According to the question ,we have

i.e.  Time taken by Beth to do a job =

Hence, the  time taken by Beth to do a job alone =  7 and 1/2 hours

the discriminant is 64 + 4*1*12 = 112

this is prime.

step-by-step explanation: