Verified answer

надо из десятичной периодической привести к обыкновенным дробям

x = 0.(7)

10x = 7.(7)

10x - x = 7.(7) - 0.(7)

9x = 7

x = 7/9

-----

3.(45) = x

100x = 345.(45)

100x - x = 345.(45) - 3.(45)

99x = 342

x = 342/99

-----

0,7(54) = x

10x = 7.(54)

1000x = 754.(54)

1000x - 10x = 754.(54) - 7.(54)

990x = 747

x = 747/990

-----

x = 4.71(63)

100x = 471.(63)

10000x = 47163.(63)

10000x - 100x = 47163.(63) - 471.(63)

9900x =  46692

x = 46692/9900