A can do one-third of a work in 15 days, B can do 75% of the same work in 18 days and C can do the same work in 36 days. B and C work together for 8 days. In how many days will A alone complete the remaining work?

Time taken by A to complete the work = 15 $$\times$$ 3 = 45 days
Time taken by B to complete the work = $$\frac{18}{75}\times$$ 100 = 24 days
Time taken by B to complete the work = 36 days
Let the total work be 360 units
($$\because$$ LCM of 45, 24 and 36 is 360.)
Efficiency of A = 360/45 = 8
Efficiency of B = 360/24 = 15
Efficiency of C = 360/36 = 10
Work done by B and C work together for 8 days = (15 + 10) $$\times 8 = 25 \times 8 = 200 units$$
Remaining work = 360 - 200 = 160 units
Time taken b A to complete the remaining work = 160/8 = 20 days