Explicación paso a paso:
[tex]( \frac{1}{2} - \frac{1}{4} ) + ( \frac{1}{3} - \frac{1}{4} ) \\ \frac{1}{2} \times \frac{2}{2} = \frac{2}{4} \\ \frac{1}{3} \times \frac{4}{4} = \frac{4}{12} \\ \frac{1}{4} \times \frac{3}{3} = \frac{3}{12} \\ ( \frac{2}{4} - \frac{1}{4} ) + ( \frac{4}{12} - \frac{3}{12} ) = \frac{1}{4} + \frac{1}{12} = \\ = \frac{3}{12} + \frac{1}{12} = \frac{4}{12} = \frac{1}{3} [/tex]
espero te sirva
