Question 330805
Remember, fraction of work = (rate/unit)(number of units)

Roma's rate is 9/2 hours to complete a job.  That means she finishes 

1/(9/2)=2/9 of the job per hour (rate/unit). Thus, in 2 hours (number of units), she completes 2(2/9)=4/9 of the job.

Therefore, there is 5/9 of the job to complete after Amor joins in.

{{{(2/9+1/t)*2=5/9}}}

{{{t=18}}} hours for Amor to complete the job alone.

So, they both can complete it together from beginning to end in

{{{2/9+1/18=1/t}}}

{{{t=18/5=3.6}}} hours working together.