This Instructional Activity is a part of the Lesson 10, Unit 4, Grade 8. Students work with proportional relationships that involve average speed and constant speed in order to write a linear equation in two variables. Students use linear equations in two variables to answer questions about distance and time. We can do several things to answer this problem, but let's begin to organize our work using a table for time and distance:Paul could walk 4 miles in 50 minutes because 50 minutes is twice the time we were given, so we can calculate twice the distance, which is 4.