From YouTube, produced by Lawrence Perez
This video indicates it is for pre-algebra, however this would be good for anyone who is reviewing or learning addition on a number line. This video shows how to add numbers using a number line, some of the numbers they use start with a negative, then they add a positive number. They show many different examples. They also use the number line to show how to find a missing addend, -10 + x = 2. Video is good quality and good for all students as review or initial learning of the concept.