Given,
A and B can finish a work in = 20 days
A can \(\frac{1}{5}\)th work in = 12 days
∴ A+ B ‘s 1 day work \(=\frac{1}{20}\)
∴ A’s 1 day work \(=\frac{1}{5\times12}=\frac{1}{60}\)
B’s 1 day work = (A+B)’s 1 day work – A’s 1 day work
\(=\frac{1}{10}-\frac{1}{60}=\frac{3-1}{60}=\frac{2}{60}=\frac{1}{30}\)
Thus B can finish the work in \(=\frac{1}{\frac{1}{30}}\) = 30 days
