Răspuns:
a=60 ; b=140 ; c=220
Explicație pas cu pas:
a, b, c d.p. cu 3, 7, 11
[tex] \frac{a}{3} = \frac{b}{7} = \frac{c}{11} = k[/tex]
a/3=k => a=3k
b/7=k => b=7k
c/11=k => c=11k
a+b+c=420 => 3k+7k+11k=420
21k=420 => k=420:21=20
a=3k=3×20=60
b=7k=7×20=140
c=11k=11×20=220
