“If we use a ruler to draw the line, we can use the line to find the cost of different numbers of muffins. See, the line shows that 4 muffins will cost $1.20. That matches the table.”

Edward studied his table and Frank's graph. “You can see the same patterns in both the table and graph. For every muffin you add to the table, the cost goes up 30¢. Each time you add a muffin to the graph, you move one to the right and the line goes up another 30¢. That's because the cost of one muffin is 30¢.”