Step-by-step explanation:
To multiply the fractions, like

Multiply the top,
then multiply the bottom.

Try to use a calculator if you aren't arithmetic heavy, but I suggest you to try to remember them because they are going to be helpful for courses like Algebra, Calculus, Statistics, etc.
To divide fractions, like

You take the top number,

Then you flip the bottom number,

Then multiply the two

And that is your answer. Comment if you need more clarification
Yes, HL would be correct.
This states that if two hypotenuses are congruent (they have the same one)
and if one pair of legs are congruent,
the figure is congruent.
I hope this helps!
~cupcake
We know, Length of Image = Length of Object * Dilation factor,
Just substitute your known values,
Length of Image = 9 * 2 = 18
In short, Your Answer would be 18 cm
Hope this helps!