In a row of 20 seats, in how many ways can 3 blocks of consecutive seats with 5 seats in each block be selected?Please explain each step in a layman`s term.Thanks.

PFA

Thank you sir for the solution and your time.I`m little confused here or perhaps obtuse because the question talks about selection.Here is what I have understood from your solution :The different positions of each block represents different blocks right? This leds to arrangement as you did in your solution . Hope my understanding is correct .

Placement of those blocks will actually mean that you have selceted those 5 consecutive chairs at different positions.