Math - Expanded Method in Addition
http://www.educreations.com/lesson/view/expanded-method-in-addition/14708020/?ref=link
http://www.educreations.com/lesson/view/expanded-method-in-addition/14708020/?ref=link
Making a Proof Drawing for Subtraction with Regrouping
http://www.educreations.com/lesson/view/proof-drawing-for-sub-w-regrouping/14758405/?ref=link
http://www.educreations.com/lesson/view/proof-drawing-for-sub-w-regrouping/14758405/?ref=link