Find the first 4 terms, in ascending powers of $x$, of the binomial expansion of

$${\left(3-\frac{x}{9}\right)}^9$$

giving each term in its simplest form.

Hence find the constant term in the series expansion of

$${\left(2+\frac{1}{x}\right)}^2{\left(3-\frac{x}{9}\right)}^9$$