$ \begin{array}{r|l} 6 & 2\\ 3 & 3\\ 1 & \end{array} $
6 = 2 * 3 * 1
$ \begin{array}{r|l} 15 & 3\\ 5 & 5\\ 1 & \end{array} $
15 = 3 * 5 * 1
НОК (6; 15) = 3 * 5 * 2 = 30

$ \begin{array}{r|l} 24 & 2\\ 12 & 2\\ 6 & 2\\ 3 & 3\\ 1 & \end{array} $
24 = 2 * 2 * 2 * 3 * 1
$ \begin{array}{r|l} 18 & 2\\ 9 & 3\\ 3 & 3\\ 1 & \end{array} $
18 = 2 * 3 * 3 * 1
НОК (24; 18) = 2 * 2 * 2 * 3 * 3 = 72