![\"\"](\"/userfiles/image/steps_images/step1.JPG\")
Observe from the figure,
\The set A contains 25 elements, then ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=3b36f0271b69fb1a9f6bcfe9bc5f7de3.png\")
.
The set B contains 20 elements, then ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=a0cc064ee24680b733c8b5fdfdc78cc1.png\")
.
The common part of set A and set B contains 8 elements, then ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=facbe3d93deaaca64affa6bb1b259ff4.png\")
.
The elements in the set A or set B is ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=b82b5bd538d15c74421b62868fe989db.png\")
.
Use counting formula : ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=d815ae311a304037d826dfdc6a3b5a04.png\")
.
Substitute ![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=3b36f0271b69fb1a9f6bcfe9bc5f7de3.png\")
, ![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=a0cc064ee24680b733c8b5fdfdc78cc1.png\")
and ![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=facbe3d93deaaca64affa6bb1b259ff4.png\")
in the formula.
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=c7d7fa583a80c5ddd3471521af8f143f.png\")
![\"\"](\"/userfiles/image/steps_images/solution.JPG\")
The elements in the set A or set B is 37.