title: How do I check if a given string from a user is a valid arithmetic equation?
body: <p>I need to accept a string from a user.</p>
  
  <p>Something like <code>(2*34)+96/2*6-98</code>
  and not an illegal string like <code>4*(2*aggw*^^)*as.,,;</code></p>
  
  <p>I need to verify if it is a valid arithmetic equation.</p>