The first thing to go for is slope. Is there a consistent slope? To find out, take matching pairs of x and y values. The slope, if there is a consistent one, is the difference between the y values divided by the difference of the matching x values. (14-8)/(6-4), (20-14)/(8-6), (32-20)/(12-8). Each of these fractions gives the number 3 (6/2, 6/2, 12/4). So the slope is 3. The linear equation is y=3x+b, where b is the y intercept and 3 is the slope. To find b we simply put in one x and matching y value: let's go for the smallest when x=4, y=8. 8=3*4+b. So b=8-12=-4. The equation becomes y=3x-4. Let's see if other values fit. What is y when x is 8? y=24-4=20, which matches the given data. The domain of the function given the data is x between 4 and 12 and the range (y) is between 8 and 32.