if 30 men can do a job in 39 days fund the part of the job that can be completed by 1 man in 1 day

Hi Gopika,
Always remember that MxDxH/W = k (constant) [ where M,D,H are men, days, hours per day and W is work, drop H if hours worked per day are not defined]
Therefore, M1xD1/W1 = M2xD2/W2
M1 = 30, D1 = 39, W1 =1 (as work was completed)
M2 = 1, D2 = 1, W2 = unknown
You get W2 = 1/1170(1/30x39)
This is the part of job done by one man in one day.