1) 0,25a=0,20b => a/4=b/5=k (egalam sirul de rapoarte cu un numar k)
a=4k si b=5k
inlocuim in relatia data 12k+10k-6=60 => 22k=66 => k=3 deci a=12 si b=15
2) x/7=y/11=z/5=k => x=7k, y=11k si z=5k
x+y+z=2530
inlocuim in suma lor si obtinem 7k+11k+5k=2530 => 23k=2530 => k=110
=> x=7x110=770 lei y=11x110=1210 lei si z=5x110=550 lei