To find what percent $x$ is less than $y$, we can follow these steps:
1. Express $y$ in terms of $x$

The problem states that $y$ is $80 %$ greater than $x$. This can be written as:

$$
\(y=x+0.80 x=1.8 x\)
$$

2. Determine the difference

The difference between $y$ and $x$ is:

$$
\(\text { Difference }=y-x=1.8 x-x=0.8 x\)
$$

3. Calculate the percentage less than $y$

To find what percent $x$ is less than $y$, we use the formula:

$$
\(\text { Percent Less }=\left(\frac{\text { Difference }}{\text { Base Value }}\right) \times 100 \)%
$$


Here, the base value is $y$ because we are comparing $x$ to $y$ :

$$
\(\text { Percent Less }=\frac{y-x}{y} \times 100\) %
$$

Substitute $y=1.8 x$ into the equation:

$$
\(\begin{gathered}
\text { Percent Less }=\frac{0.8 x}{1.8 x} \times 100 % \\
\text { Percent Less }=\frac{0.8}{1.8} \times 100 % \\
\text { Percent Less }=\frac{8}{18} \times 100 \%=\frac{4}{9} \times 100 %
\end{gathered}\)
$$

4. Convert the fraction to a percentage

Since $\(\frac{1}{9} \approx 11.11 \ldots \)%$, then $\(\frac{4}{9}\)$ is:

$$
\(4 \times 11 \frac{1}{9} \%=44 \frac{4}{9}\) %
$$


Correct Option: D. $\(44 \frac{4}{9}\)$