This Instructional Activity is a part of the Lesson 28, Unit 4, Grade 8. Systems of linear equations can be solved by sketching the graphs of the lines defined by the equations of the system and looking for the intersection of the lines, substitution (as was shown in the last lesson), or elimination (as was shown in this lesson). Some systems can be solved more efficiently by elimination, while others by substitution. Which method do you think would be most efficient for the following system? Explain.