Rafiq can do in 1 day=110 portion of work
Rafiq can do in 6 days =610=35 portion of work
Shafiq can do in 1 day= 120 portion of work
Shafiq can do in 4 days = 420=15 portion of work
Rafiq & Shafiq completed in first 6 days= 35+15=45 portion of work
So, the remaining work = (1-45)=15 portion of work
Arif can do in 1 day =110 portion of work
Arif can do 110 portion in 1 day
Arif can do 15 portion in = 105=2 days
The required time for completion of the work=6+2=8 days ans.