Asif can do a job 15 hours, and Russel can do the same job in 9 hours. If they start doing the job together at 6 am. At what time will Asif finish the job?

Asif  does in 1 hour does 1/15 part of the work Asif  does in 3 hour does 3/15 or 1/5 part of the work Russel  does in 1 hour 1/9 part of the work Russel  does in 1 hour 3/9 or 1/3 part of the work both of them together do (1/5+1/3) part of work=8/15 part of work work remaining = (1-8/15)=7/15  part of work asif does 1 or full part in 15 hours Asif does 7/15 part  15x7/15=7 hours so , work will finish at = 9a.m+7 hr=4 pm