3,212:4/5= 43,75. 2/35= 1,5/3,2 + 1,9/9,6=

$3,212:\frac{4}{5}=3,212:0,8=4,015$

или

$3,212:\frac{4}{5}=3\frac{212}{1000}:\frac{8}{10}=\frac{3212}{1000}:\frac{8}{10}=\frac{3212}{1000}\cdot\frac{10}{8}=\frac{803}{200}=4\frac{3}{200}$

$43,75\cdot\frac{2}{35}=\frac{43,75\cdot2}{35}=\frac{87,5}{35}=2,5$

$1,5:3,2+1,9:9,6=\frac{2}{3}$

1) $1,5:3,2=1\frac{5}{10}:3\frac{2}{10}=1\frac{1}{2}:3\frac{1}{5}=\frac{3}{2}:\frac{16}{5}=\frac{3}{2}\cdot\frac{5}{16}=\frac{15}{32}$

2) $1,9:9,6=1\frac{9}{10}:9\frac{6}{10}=\frac{19}{10}:9\frac{3}{5}=\frac{19}{10}:\frac{48}{5}=\frac{19}{10}\cdot\frac{5}{48}=\frac{19}{96}$

3) $\frac{15}{32}+\frac{19}{96}=\frac{45+19}{96}=\frac{64}{96}=\frac{2}{3}$