### Solution:

Concept- A, B and C working together can finish a piece of work in 8 hours. A alone can do it in 20 hours and alone can do it in 24 hours.We first determine how much work each person completed in an hour separately using the unitary technique. First, we must determine how much work each candidate completed in an hour (A and B as C is not given). After that, we must compare the total amount of work completed by all candidates in an hour to the time taken for A, B, and C to collaborate.

The work completed in an hour by each candidate is listed as follows:

where are the applicants and their tasks completed in an hour.

A's one-worth hour's of work is B's one-worth hour's of work is C's one-worth hour's of work is The work completed in an hour by each candidate is listed as follows:

Now, dividing the total amount of work (8 hours) by one hour, we arrive at the following: of all the work done.

$x=30$ hours

C alone, the task will be finished in 30 hours

Hence, the answer is 30 hours.

Syllabus: CBSE