1)x+y=20
0,25=25/100=1/4
0,(3)=3/9=1/3
{x,y}ip{1/4,1/3}
x/4=y/3=k
x=4k
y=3k
4k+3k=20
7k=20
k=20/7
x=4k=(4·20)/7=80/7
y=3k=(3·20)/7=60/7
2)(x+y+z)/3=60
x+y+z=60·3
x+y+z=180
0,(3)=3/9=1/3
0,25=25/100=1/4
0,2=2/10=1/5
{x,y,z}ip{1/3, 1/4, 1/5}
x/3=y/4=z/5=k
x=3k
y=4k
z=5k
3k+4k+5k=180
12k=180
k=180/12
k=15
x=3k=3·15
x=45
y=4k=4·15
y=60
z=5k=5·15
z=75
s.a.m.d