a) [tex]\frac{5}{3} + \frac{1}{3} + \frac{2} {3} = \frac{8}{3}[/tex]
b) [tex]\frac{15}{7} + (\frac{8}{7} + \frac{2}{7}) = \frac{15}{7} + \frac{10}{7} = \frac{25}{7}[/tex]
c) [tex](\frac{11}{2}- \frac{10}{2}) + (\frac{5}{2} - \frac{4}{2}) = \frac{1}{2} + \frac{1}{2} = \frac{2}{2} = 1[/tex]
