a/2=b/3=c/5=k
a=2k
b=3k
c=5k
k^2+4k^2+9k^2=56
14k^2 = 56
k=2
a=4
b=6
c=10
b)pretul initial P
dupa prima scumpire P1
P1 = P+10P/100 =110P/100
dupa a doua scumpire P2
P2 = 423,5 = 110P1/100 = 11^2 P/100
P = 42350/11^2 = 350 lei
P2-P=423,5 - 350=73,5 lei
73,5 = p x P/100
p = 7350/350
p=21%