The data is not linear. From (3, 1) to (7, 2), we add 4 to the x-value and add 1 to the y-value. This pattern continues for a little while, however, from (11, 3) to (18, 5), we add only 7 to the x-value even though we added 2 to the y-value. Given this information, we can determine that this is not linear data.
