pake cara tolong.....

pekerja A
80% = 20 hari
20% = 5 hari

pekerja A + B = 3 hari

pekerja B
1/3 = 1/5 + 1/B
5/15 = 3/15 + 1/B
1/B = 5/15 - 3/15
1/B = 2/15
B = 15/2 = 7hari 12jam

semoga membantu :)