Answer:
Explanation:
Work finished by Francesca in one hour = 1/6
Work finished by Irvin in one hour = 1/4
Work finished by Francesca and Irvin in one hour = 1/6 +1/4

5/12 of the work is completed by both in an hour
Whole work will be completed in 1*12/5 =12/5 hours = 2 2/5 hours
= 2 hours 24 minutes