Tri-Triangles is a 'Problems of the Month' activity. It provides five different triangle activities focusing on Patterns and Algebraic Thinking. The activities range from Level A (challenging for 2nd to 3rd graders) to a Level E (challenging for HS students). Instructions and student masters are provided for each activity level. The activities encourage problem solving skills. The activities are well-written and provide appropriately leveled challenges. Alignment with Common Core State Standards is provided. Students are expected to discuss and justify their solutions. Although answer keys are not provided, student discussion should lead to appropriate solutions.