[tex]\frac{1}{2x}+\frac{1}{3x}+\frac{1}{6x}-\frac{1}{x} =[/tex]
[tex]=\frac{3}{6x}+\frac{2}{6x}+\frac{1}{6x}-\frac{6}{6x}[/tex]
[tex]=\frac{3+2+1-6}{6x}[/tex]
= 0
