Andi dan Dian bekerja bersama-sama dapat menyelesaikan sebuah pekerjaan selama 4 hari. Dian dan Toto bekerja bersama-sama dapat menyelesaikan pekerjaan yang sam

Misal Andi = a, Dian= b, dan Toto= c

1/a + 1/b = 1/4
1/b + 1/c = 1/3
1/a + 1/c = 1/2,4 = 5/12

1/a+1/b= 1/4
1/b = 1/4-1/a

1/b + 1/c = 1/3
1/b = 1/3 - 1/c

1/a + 1/c = 5/12
1/a = 5/12 - 1/c

1/b = 1/4 - 1/a
1/3 - 1/c = 1/4 - (5/12 - 1/c)
1/3 - 1/c = 1/4 - 5/12 + 1/c
1/3 - 1/c = 3/12 - 5/12 + 1/c
1/3 - 1/c = -2/12 + 1/c
1/3 + 2/12 = 1/c + 1/c
6/12 = 2/c
1/2 = 2/c
c= 2×2
c = 4 

1/b = 1/3 - 1/c
1/b = 1/3 - 1/4
1/b = 4/12 - 3/12
1/b = 1/12
b = 12

Jadi, Dian dpat melaksanakan pekerjaan tersebut selama= 12 hari <----- jawaban