0.(3)=3/9=1/3
0.2=2/10=1/5
0.25=1/4
x, y, z direct proportionale cu 1/3, 1/5 si 1/4, rezulta ca 3x=5y=4z
x=k/3
y=k/5
z=k/4
xy+yz+zx=45
k/3·k/5+k/5·k/4+k/4·k/3=45
k²/15+k²/20+k²/12=45
4k²/60+3k²/60+5k²/60=45
12k²/60=45
k²/5=45
k²=225
k=15
x=k/3=15/3=5
y=k/5=15/5=3
z=k/4=15/4
