**This information is given:** Mrs. Fitzgerald planted a tree. After 10 days, the tree measured 39 inches tall. After 28 days, the tree measured 51 inches tall.

**This is what I did:** Since we are given two points, I found the slope. To find slope between two points, you find the change in y over the change in x. Therefore, the two changes are 28-10 and 51-39.

\*UPDATE: I have caught my mistake: for some odd reason, I thought that time was the dependent variable, though I know that it really is the independent. I apologize for my silly mistake :)

***What I am confused about:*** I first wrote down that the change in y is 28-10, since they are the days. In this circumstance, days (time) is the dependent variable. Therefore, they are the y-coordinates. Similarly, 51-39 are the inches, and inches is the independent variable, which makes the 51 and 39 the x-coordinates. However, my friend believes that it is the other way around - 28-10 is the change in x and 51-39 is the change in y; however, I don't understand why this would be. 

*Who is correct? If my friend is correct, why is that?*