Prabhat has done 1/2 of job in 12 days. Prabhat has done in 1/24 part of job in 1 day. Santhosh complete rest (1/2) part of job in 6 days. Santhosh has done in 1/12 part of job in 1 days. Santhosh and Prabhat complete part of job in 1 day = (1/24) + (1/12) = 1/8 Santhosh and Prabhat complete 1/8 part of job in 1 day. Santhosh and Prabhat will complete job in 8 day.