Question 913229
Ed can do a job in 4 days.

so he does 1/4 of the job in 1 day

 When Ed and Maymay work together, it would take them 2 1/3 days. 

so they together do 3/7 of the job in 1 day

Maymay will do 3/7 - 1/4 of the job in 1 day

=(12-7)/28 
=5/28 of the job in 1 day

so Mayamy will take 28/5 days to complete the job alone

5.6 days