a) 2/5 + 3/5 = 5/5 = 1
b) 1/3 + 1/6 = 2/6 + 1/6 = 3/6 = 1/2
c) [tex]\frac{3}{4} * \frac{5}{7} = \frac{3*5}{4*7} = \frac{15}{28}[/tex]
