Answer:
The set A = { 1,2,3,4,5,6,7,8,9}
Step-by-step explanation:
<u><em>Step(i):-</em></u>
Given that the set 
  { x/x/ is a natural number less than 10 }
<u><em>Natural numbers :</em></u>
The natural numbers are 
           { 1,2,3,4,5,6,7,8,9,10,.........}
The set A =  { x/x/ is a natural number less than 10 }
The set A = { 1,2,3,4,5,6,7,8,9}