In the lesson linked below, students will trade equivalent pattern blocks to understand the concept of substitution. Students will compare slopes and y-intercepts of graphs that meet at one point, are the same line and are parallel to discover the number of solutions for a system linear equations without graphing.
Lesson guidelines: http://auhsdmath.pbworks.com/w/file/fetch/60768766/5_0Teach_Dir_Systems%282%29.pdf
Patterns handout: http://auhsdmath.pbworks.com/w/file/fetch/60768796/5_2Patterns_Linear_Systems%282%29.pdf
Thinking map: http://auhsdmath.pbworks.com/w/file/fetch/60768816/5_3ThinkingMap%282%29.pdf