Direct and Inverse Proportion

Eighteen workers are scheduled to complete a project in \(20\) days. After working for \(5\) days, \(6\) workers leave.

1. Find how many additional days the remaining workers need.

2. Find the delay relative to the original schedule.

3. Instead, suppose replacement workers can join immediately after day \(5\). What is the minimum number of additional workers needed then to finish by the end of day \(18\)?