title: Finding Prime numbers in a vector and print them in revers in another vector
body: <p>here's the problem: 
  x is a vector with n elements.. build another vector, y, which will contain prime elements from x, but in reverse order.
  My code. Don't know what I'm doing wrong.</p>
  
  <p><a href="https://i.stack.imgur.com/nFrg5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nFrg5.png" alt="Vs code"></a></p>