[SAS Program]              
               
data rsq;
input gpa greq grev mat ar;
cards;
3.2 625 540 65 2.7
4.1 575 680 75 4.5
3.0 520 480 65 2.5
2.6 545 520 55 3.1
3.7 520 490 75 3.6
4.0 655 535 65 4.3
4.3 630 720 75 4.6
2.7 500 500 75 3.0
3.6 605 575 65 4.7
4.1 555 690 75 3.4
2.7 505 545 55 3.7
2.9 540 515 55 2.6
2.5 520 520 55 3.1
3.0 585 710 65 2.7
3.3 600 610 85 5.0
3.2 625 540 65 2.7
4.1 575 680 75 4.5
3.0 520 480 65 2.5
2.6 545 520 55 3.1
3.7 520 490 75 3.6
4.0 655 535 65 4.3
4.3 630 720 75 4.6
2.7 500 500 75 3.0
3.6 605 575 65 4.7
4.1 555 690 75 3.4
2.7 505 545 55 3.7
2.9 540 515 55 2.6
2.5 520 520 55 3.1
3.0 585 710 65 2.7
3.3 600 610 85 5.0
;
proc reg;
  model gpa = greq grev mat ar / selection=rsquare;
run;

[SAS Output]


  N = 30     Regression Models for Dependent Variable: GPA


Number in     R-square   Variables in Model
  Model

      1     0.38529398   AR
      1     0.37350131   GREQ
      1     0.36509196   MAT
      1     0.33808659   GREV
 ----------------------------
      2     0.58300302   GREQ MAT
      2     0.51549156   GREV AR
      2     0.50329629   GREQ AR
      2     0.49347870   GREV MAT
      2     0.49232208   MAT AR
      2     0.48524079   GREQ GREV
 ---------------------------------
      3     0.61704497   GREQ GREV MAT
      3     0.61020192   GREQ MAT AR
      3     0.57187378   GREV MAT AR
      3     0.57160608   GREQ GREV AR
 ------------------------------------
      4     0.64047409   GREQ GREV MAT AR
 ----------------------------------------