1]A and B together can do a work in 8 days.If A alone can do it in 12 days,then in how many days can B alone do it?

time for [A + B]'s days 1 work = 1/8
time for A's days 1 work =  1/12
time for B's days 1 work = ?

Time of [A+B]'s 1 day work = Time of A's 1 day work + Time of B's 1 day work
1/8 = 1/12+ B
B = 1/8 - 1/12 = 1/24

B's 1 days work = 24 days