Khan Academy
Khan Academy: Find Missing Number (Add and Subtract Within 20)
Learn how to solve problems like "___ - 7 = 18" where you don't know one of the values in an addition or subtraction equation. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or...
CK-12 Foundation
Ck 12: Elem Math: Calculating Sums: Less Than, Greater Than, or Equal To
[Free Registration/Login may be required to access all resource tools.] Locate the video "Calculating Sums: Less Than, Greater Than, or Equal to." In this learning module, students apply their addition and subtraction skills in comparing...