Simple Crypt-Addition

Here are four different arithmetic crypt problems for you to figure out. Each letter represents a different digit, and each problem is independent from each other problem. These are simple enough that you should be able to figure them out in your head, which means that they should also be great for introducing young puzzlers to cryptographic math puzzles.

   Y
   Y
 + Y
  MY
  

   XXX
 +   B
  BAAA
  

  ON
  ON
  ON
+ ON
  GO
  

  MA
 + A
  AM


For more puzzles like this get Brainteasers and Mindbenders by Ben Hamilton.