title: How to do subtraction in strings
body: <p>How do you print addition in python?
  I tried to  define addition and tell it to print:</p>
  
  <p><code>subtraction = int(number - reverse(number))
   print str(subtraction)</code></p>
  
  <p>But it always says:</p>
  
  <p><code>Traceback (most recent call last):
    File "C:\Python25\Castor's Python Programs\proj02.py", line 16, in &lt;module&gt;
      subtraction = int(number - reverse(number))
  TypeError: unsupported operand type(s) for -: 'str' and 'str'</code></p>
  
  <p>This is my full code:</p>
  
  <pre><code>import sys
  def reverse(num):
          return (num)[::-1]
  
  print "This is a puzzle favored by einstein. You will be asked to enter a three digit number, where the hundred's digit differs from the ones digit by at least two. The procedure will always yield 1089."
  number = raw_input("Give me a number:")
  print "For the number: "
  print number
  print " the reverse number is: "
  print reverse(number)
  print "The difference between "
  print number
  print" and "
  print reverse(number)
  print " is "
  subtraction = int(number - reverse(number))
  print  str(subtraction)
  print "The reverse difference is: "
  print  str(reverse(subtraction))
  print "The sum of: "
  print subtraction
  print " and revDiff is: "
  finaladdition = int(subtraction - reverse(subtraction))
  print str(finaladdition)
  </code></pre>
  
  <p>Can someone please help?</p>