[tex]\frac{1}{48} + \frac{1}{5} -\frac{1}{6} = \frac{5+48-40}{240} =\frac{13}{240}[/tex] (am adus la acelasi numitor, acesta fiind 240)
[tex]\frac{1}{12} +\frac{1}{30} -\frac{2}{15} = \frac{30+12-24}{360} =\frac{18}{360} =\frac{1}{20}[/tex] (numitorul comun=360, iar la final am simplificat) ;)