Aflati numerele a ,b si c daca sunt direct proportionate cu 2 , 5 si respectiv 7 si a+b+c=28. a.................2 b.................5 c.................7 a+b+c=28 a/2 =b/5=c/7 a=2k b=5k c=7k 2k+5k+7k=28 14k=28/:14 k=2 a=2k-->a=4 b=5k-->b=10 c=7k--->c=14
