To overlay the regression line and the scatter diagram for the data, you must first set up the scatter diagram by pressing 2ndF 
STAT PLOT , touching
A PLOT1, pressing ENTER 
ENTER
▼ 
▼
ENTER 
▼ 
2ndF 
L1 
ENTER
2ndF 
L2 
ENTER 
2ndF 
STAT PLOT , touching G S.D., and touching 3 Scattr.
Display the scatter diagram for the data (Please refer to Chapter 7 for discussion of how to display a scatter diagram) by pressing WINDOW and setting Xmin = 20, Xmax = 45, Xscl = 5, Ymin = 25, Ymax = 40, and Yscl = 5. Press GRAPH to view the scatter diagram shown below:
To view the overlay of the regression line and the scatter diagram, press Y= CL 
VARS , touch H STAT, press ENTER , touch B REGEQN, double touch 1 RegEqn, and press GRAPH . The following overlay will be displayed.
