Express in the form of .

Let

Now, … (1)

As there are three repeating digits after decimal,

Multiplying both sides of equation (1) by 10³ = 1000, we get,

1000 x = 665.665665… (2)

Subtracting equation (1) by (2)

1000 x – x = (665.665665…..) – (0.665665665…..)

999x = 665