122. A and B can do a work in 8 days, B and C can do the same work in 12 days. A, B and C together can finish it in 6 days. A and C together will do it in :

✅ The correct answer is option C.
(A + B + C)’s 1 day’s work =
1
;

6

(A + B)’s 1 day’s work =
1
;

8

(B + C)’s 1 day’s work =
1
.

12

(A + C)’s 1 day’s work

=

2 x
1

–

1
+
1

6
8
12

=

1
–
5

3
24

=
3

24

=
1
.

8

So, A and C together will do the work in 8 days.