Assume you have collected data pairs (x, y) on a certain variety of tree. x is the number of weeks since the tree was planted and y is the height of the tree in inches. A plot of the data points with the best-fit line is given below. What age is predicted by the best-fit line for a height of 50 inches? 

I'm not sure what the answers are, but I can help. If you go to the x axis and search for 50, then go straight up to the line of best fit, you'll find the estimated height of the tree. It appears to be about 70. 

Hope this helps!