The given set :
○=> {x : x = 7a, a∈N and 3 < a ≤ 7}
It is to be noted that this set is given in set builder form.
Given :
▪︎x:x = 7a.
▪︎a is a subset of natural numbers.
▪︎The numbers in the set are between 3 and 7 where we will not include 3 and 7.
Which means, the elements of this set are :
= 4, 5, 6
The above given set in roster form :
= { 4, 5, 6 }