Выполним каждое действие по порядку:
а) $$\frac{7}{16} + \frac{1}{2} = \frac{7}{16} + \frac{8}{16} = \frac{15}{16}$$
б) $$7 - 4\frac{5}{9} = 7 - \frac{4*9 + 5}{9} = 7 - \frac{41}{9} = \frac{7*9}{9} - \frac{41}{9} = \frac{63}{9} - \frac{41}{9} = \frac{22}{9} = 2\frac{4}{9}$$
в) $$\frac{11}{28} * \frac{7}{33} = \frac{11*7}{28*33} = \frac{11*7}{4*7*3*11} = \frac{1}{4*3} = \frac{1}{12}$$
г) $$\frac{3}{8} : \frac{9}{16} = \frac{3}{8} * \frac{16}{9} = \frac{3*16}{8*9} = \frac{3*2*8}{8*3*3} = \frac{2}{3}$$