Разберем каждое выражение по порядку:
1) $$35 - (-51) : 3 = 35 - (-17) = 35 + 17 = \textbf{52}$$
2) $$\frac{2}{9} \cdot 21 + \frac{5}{6} = \frac{2 \cdot 21}{9} + \frac{5}{6} = \frac{42}{9} + \frac{5}{6} = \frac{14}{3} + \frac{5}{6} = \frac{28}{6} + \frac{5}{6} = \frac{33}{6} = \frac{11}{2} = \textbf{5,5}$$
3) $$6,2 - 3,5 \cdot 2,4 = 6,2 - 8,4 = \textbf{-2,2}$$
4) $$92 - 16 \cdot (-6) = 92 - (-96) = 92 + 96 = \textbf{188}$$
5) $$\frac{3}{16} : \frac{5}{32} + 1 \frac{1}{5} = \frac{3}{16} \cdot \frac{32}{5} + \frac{6}{5} = \frac{3 \cdot 32}{16 \cdot 5} + \frac{6}{5} = \frac{6}{5} + \frac{6}{5} = \frac{12}{5} = \textbf{2,4}$$
6) $$93 : (-3,3 - 2,9) = 93 : (-6,2) = \textbf{-15}$$
7) $$84 + 5 \cdot (-13) = 84 - 65 = \textbf{19}$$
8) $$\frac{2}{15} + \frac{7}{20} : \frac{3}{16} = \frac{2}{15} + \frac{7}{20} \cdot \frac{16}{3} = \frac{2}{15} + \frac{7 \cdot 16}{20 \cdot 3} = \frac{2}{15} + \frac{28}{15} = \frac{30}{15} = \textbf{2}$$
9) $$98 : (-3,5 + 8,4) = 98 : 4,9 = \textbf{20}$$
10) $$28 - 18,7 = \textbf{9,3}$$
11) $$2 - \frac{22}{15} : \frac{33}{35} = 2 - \frac{22}{15} \cdot \frac{35}{33} = 2 - \frac{22 \cdot 35}{15 \cdot 33} = 2 - \frac{2 \cdot 7}{3 \cdot 3} = 2 - \frac{14}{9} = \frac{18}{9} - \frac{14}{9} = \frac{4}{9} \approx \textbf{0,44}$$
12) $$(2,3 - 7,1) : 0,4 = -4,8 : 0,4 = \textbf{-12}$$