Description for Correct answer:
Let the required number of days be x.

Remaining work = \( \Large 1-\frac{5}{8}=\frac{3}{8} \)

Less work, Less days (Direct proportion)

\( \Large \frac{5}{8}:\frac{3}{8}\ ::\ 20:x \)

=> \( \Large x = \frac{3}{8} \times 20 \times \frac{8}{5} \)

Therefore, x = 12 days