If √0.09 * 0.9 * x = 0.9 * 0.09.√y , then find x/y
Do you mean that your teacher did not get sqrt y on the RHS. That her answer was just a number?
Maybe this was your intended question.
$$\begin{array}{lr}
\\\sqrt{0.09 \times 0.9 \times x} = 0.9 \times 0.09\sqrt{y}\qquad then \;find \;\frac{x}{y}\qquad &\mbox{(1)} \\\\
square\; both\; sides &\mbox{(2)} \\\\
0.09\times 0.9\times x=0.9^2\times 0.09^2\times y &\mbox{(3)} \\\\
Divide\;both\;sides\;by\;0.09\times0.9 &\mbox{(4)} \\\\
x=0.9\times 0.09y &\mbox{(5)} \\\\
Divide\; both \;sides\; by \;y &\mbox{(6)} \\\\
\frac{x}{y}=0.9\times 0.09 &\mbox{(7)} \\\\
\frac{x}{y}=0.081 &\mbox{(8)}\\\\
\end{array}$$
Does that look better Rosala? See if you can tell me what line you got lost at.
And if you can tell me why. The 1st line is just the question. Make sure it is the question that you want. 