2/3 - 1/4 : 1/6 + 1/2 =

[tex] \frac{2}{3} - \frac{1}{4} \div \frac{1}{6} + \frac{1}{2} = \frac{2}{3} - ( \frac{1}{4} \times \frac{6}{1} ) + \frac{1}{2} = \frac{2}{ 3} - \frac{3}{2} + \frac{1}{2} = \frac{4}{6} - \frac{9}{6} + \frac{3}{6} = - \frac{2}{6} = - \frac{1}{3} [/tex]