х = 0,(27) <=> 100х = 27,(27) <=> 100х - 27 = 0,(27) <=> 100х - 27 = х <=> 99х = 27 <=> х = 27/99 = 3/11

х = 1,0(1) <=> 10х - 10 = 0,(1) <=> 0,(1) = y, 10x - 10 = y <=> 10y - 1 = y, x = (y + 10)/10 <=> y = 1/9 => x = 91/90 = 1 1/90

x = 1,5(4) <=> 10x - 15 = 0,(4) <=> 0,(4) = y, 10x - 15 = y <=> 10y - 4 = y, x = (y + 15)/10 <=> y = 4/9 => x = 139/90 = 1 49/90

x = 8,7(5) <=> 10x - 87 = 0,(5) <=> 0,(5) = y, 10x - 87 = y <=> 10y - 5 = y, x = (y + 87)/10 <=> y = 5/9 => x = 788/90 = 8 34/90