notam nr cu a,b,c
{a,b,c} i.p. {2,4,7} => 2a=4b=7c=k
k-coeficient de proportionalitate
c-a=60=>c=a+60
2a=k=>a=k/2
4b=k=>b=k/4
7c=k=>c=k/7
c=a+60
k/7=k/2+60 (aduci la acelasi numitor-14)
2k/14=7k/14+60
2k/14-7k/14=60
-5k/14=60
-5k=14×60
-5k=840
k=-168
a=k/2=>a=-168/2=>a=-84
b=k/4=>b=-168/4=>b=-42
c=k/7=>c=-168/7=>c=-24
