3,(8)=3 9/10
1,(81)=1 41/50
0,1(6)= 17/100
0,2(15)=1/5
1)х= 3,888...
10х=38,88...
9х=34,992
х=3,888...
2)х=1,8181
100х=181,81
99х=179,9919
х=1,8181
3)х=0,1666
10х=1,666
100х=16,66
90х=14,994
х=0,1666
4)х=0,21515
10х=2,1515
1000х=215,15
990х=212,9985
х=0,21515