The expression is .
Below figure shows the solution using a "TI-84 plus graphing calculator".
Check the solution by substituting n = 60 and j = 20 in the formula .
The value of .
![\"\"](\"/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=51d85d3097b66045f1698cd28da1b251.png\")
.![\"TI-84](\"/userfiles/image/Library/Pre%20Calculus/TI-84_graphing_calculator_60_nCr_20.gif\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=0c1c21366e579a9ef1382622bd571b94.png\")
![\"\"](\"/userfiles/image/steps_images/step2.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=c3eeade52ab959df19db8a5ddcaf6d9e.png\")
.![\"\"](\"/userfiles/image/steps_images/solution.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=b830328c415edb8973cf057c6fb4c934.png\")
.