Recall that
[tex] \sqrt{ab}=\sqrt{a}\sqrt{b} [/tex]
To use
[tex] \sqrt{45}=\sqrt{9\cdot 5}=\sqrt{9}\sqrt{5} = 3\sqrt{5} [/tex]
So, you have
[tex] 11\sqrt{45}-4\sqrt{5} = 33\sqrt{5}-4\sqrt{5} = 29\sqrt{5} [/tex]
