Recuerda elegir una respuesta como la mejor, así agradecemos a los usuarios que se preocuparon por solucionar tu problema. saludos

Descomponemos los numeros en sus factores primos

15.I3.....21.I3....28.I2

..5I.5......7.I.7....14.I.2

..1..........1..........7.I.7

..........................1

15=3x5

21= 3x7

28= 2²x7

m.c.m (15, 21, 28) =2²x3x5x7 =420

m.c.d (15, 21, 28) =1

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Bueno

el MCM es 420

el MCD es 1

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