\|18-\|8÷2
=3\|2-2\|2÷2
=3\|2-\|2
=2\|2
[tex]\it \sqrt{18}-\sqrt8:2=\sqrt{9\cdot2}-\sqrt{8\cdot2}:2=3\sqrt2-2\sqrt2:2=3\sqrt2-\sqrt2=2\sqrt2[/tex]