Surds question grade 10

Question

I am a student and need help answering this question. I need a step by step solution.

Simplify:

$ \sqrt {18}$ - $ \sqrt {9}$

What I tried:

($ \sqrt {9}$ × $ \sqrt {2}$) - 9

= (3$ \sqrt {2}$ ) - 9

I don't know what to do next.

Thank you and help is appreciated.

Answer 1

this is $$\sqrt{2\cdot 9}-\sqrt{9}=3\sqrt{2}-3$$

Answer 2

Here is a mistake you've made:

Going from the first step to the second step, you should have put the square root: $$\sqrt{18}-\sqrt{9} \implies (\sqrt{9}\times \sqrt{2})-\color{red}{\sqrt{9}}$$ Can you take it from here?