title: Boolean method 'Blackjack' for arrays
body: <p>I'm trying to write a boolean method that checks if  a sum of integers in an array equals 21. Here's the code:</p>
  
  <pre><code>def twenty_one? (*arr) 
    arr.inject(0){|sum,x| sum + x }
    arr.eql? (21)
  end
  </code></pre>
  
  <p>But if I check </p>
  
  <pre><code>puts twenty_one?(19, 2)
  </code></pre>
  
  <p>it returns <code>false</code>, even though I tried some others too. What am I missing in this code?</p>