Bună!
a)
[tex] \frac{1}{3} + \frac{1}{4} + \frac{1}{5} + \frac{2}{3} + \frac{3}{4} + \frac{4}{5} = \\ \frac{1 + 2}{3} + \frac{1 + 3}{4} + \frac{1 + 4}{5} = \\ \frac{3}{3} + \frac{4}{4} + \frac{5}{5} = \\ 1 + 1 + 1 = \\ 3[/tex]
b)
[tex] \frac{5}{2} + \frac{7}{3} + \frac{11}{6} - \frac{3}{2} - \frac{4}{3} - \frac{5}{6} = \\ \frac{5 - 3}{2} + \frac{7 - 4}{3} + \frac{11 - 5}{6} = \\ \frac{2}{2} + \frac{3}{3} + \frac{6}{6} = \\ 1 + 1 + 1 = \\ 3[/tex]
