Răspuns:
a/3=b/7 => 7a=3b=>a=3b/7
b/7=c/8=>8b=7c=>c=8b/7
2a+5b-4c=2(3b/7)+5b-4(8b/7)=6b/7 +5b-32b/7 (amplificam pe 5b cu 7)=(6b+35b-32b)/7=9b/7
9b/7=108
9b=7×108
9b=756
b=756/9=84
a=3b/7=3×84/7=36
c=8b/7=8×84/7=96
