The Minnesota School Mathematics and Science Teaching (MINNEMAST) Project is characterized by its emphasis on the coordination of mathematics and science in the elementary school curriculum. Units are planned to provide children with activities in which they learn various concepts from both subject areas. Each subject is used to support and reinforce the other where appropriate, with common techniques and concepts being sought and exploited. Content is presented in story fashion. The stories serve to introduce concepts and lead to activities. Imbedded in the pictures that accompany the stories are examples of the concepts presented. This unit provides students with a graphic method of addition which is useful both as a checking device and as an advance in what the student did in Unit 16. Three different techniques of using graphs and linear functions for addition are presented. This approach integrates ideas of geometric symmetry and with number relationships under addition and subtraction. Worksheets and commentaries to the teacher are provided and additional activities are suggested. (JP)