Question

mmc de6,8,20 o mmc de 1,8,21 e o mmc de 6,9,15,20

Answer 1

6,8,20= 120
1,8,21=168
6,9,15,20=180

Answer 2

6, 8, 20|2
3, 4, 10|2
3, 2,  5|2
3, 1,  5|3
1, 1,  5|5
1, 1,  1       2.2.2.3.5=120

1, 8, 21|2
1, 4, 21|2
1, 2, 21|2
1, 1, 21|3
1, 1,  7|7
1, 1,  1        2.2.2.3.7=168

6, 9, 15, 20|2
3, 9, 15, 10|2
3, 9, 15,   5|3
1, 3,  5,    5|3
1, 1,  5,    5|5
1, 1,  1,    1           2.2.3.3.5=180