No.
It is: 0666/10000 = 333/5000 in its lowest terms
0.0666 is a fraction. It is a fraction in decimal form rather than in the form of a ratio. However, that does not stop it being a fraction. Its rational equivalent is 666/10000 which can be simplified. But simplification will mean that you lose information about the precision of the fraction.
804 - 186 = 618
If that's 6/18, try 1/3 and 2/6
3n = 618 n = 618 ÷ 3 n = 206
4x-618 = -614
It is: 618 = DCXVIII
0.0065
618 = 1,854/3
6.18 = 618/100 = 309/50 6.18 = 618/100 = 309/50 6.18 = 618/100 = 309/50 6.18 = 618/100 = 309/50
453 - 618 in regrouping = -165
6 divided 618 = 0.009708737864077669