title: Logic behind modular function
body: <p>I do not understand why mysteryfunction(y) will equate to 40
  when i int mysteryFunction(int, int =2). Anyone can explain to me? </p>
  
  <p>Best, MM</p>
  
  <pre><code>#include &lt;iostream&gt;
  using namespace std;
  
  int mysteryFunction (int, int = 2);
  
  int main()
  {
      int x = 10, y = 20;
      cout &lt;&lt; mysteryFunction (y); 
  
  }
  
  int mysteryFunction (int x, int y)
  {
     return x * y;
  } 
  </code></pre>