Correct Answer: Option A
2(A + B + C)'s 1 day's work = (1/30 + 1/24 + 1/20) = 15/120 = 1/8.
Therefore, (A + B + C)'s 1 day's work = 1/(2×8) = 1/16.
Work done by A, B, C in 10 days =10/16 = 5/8.
Remaining work = (1 - 5/8) =3/8.
A's 1 day's work = (1/16 – 1/24) = 1/48.
Now, 1 work is done by A in 1 day.
So, 3/8 work will be done by A in (48 x 3/8) = 18 days.
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