НОК ( 21; 28 ) = 84
------------
21 = 3 * 7
28 = 2 * 2 * 7
НОК ( 21 ; 28 ) = 3 * 7 * 2 * 2 = 84
=========================
НОК ( 18 ; 72 ) = 72
---------
18 = 2 * 3 * 3
72 = 2 * 2 * 2 * 3 * 3
НОК ( 18 ; 72 ) = 2 * 2 * 2 * 3 * 3 = 72
==========================
НОК ( 3 ; 5 ; 25 ) = 75
3 = 3
5 = 5
25 = 5 * 5
НОК ( 3 ; 5 ; 25 ) = 3 * 5 * 5 = 75