Вычислите (1;2; 4)........

$(42frac{5}{12}-21 frac{11}{18})-(25-4 frac{1}{9})=$
$42 frac{5}{12}-21 frac{11}{18}= 42frac{15}{36}-21 frac{22}{36}=41 frac{51}{36}-21frac{22}{36}=20 frac{29}{36}$
$25-4 frac{1}{9}=24 frac{9}{9}-4 frac{1}{9}=20 frac{8}{9}$
$20 frac{29}{36}-20 frac{8}{9}=20 frac{29}{36}-20 frac{32}{36}=-(20 frac{32}{36}-20 frac{29}{36})=- frac{3}{36}= -frac{1}{12}$
$(2 frac{1}{2}:3 frac{2}{3}):(7 frac{1}{2}:7 frac{1}{3})*(5 frac{1}{4}* frac{4}{21})$
$2 frac{1}{2}:3 frac{2}{3}= frac{5}{2}: frac{11}{3}= frac{5}{2}* frac{3}{11}= frac{15}{22}$
$7 frac{1}{2}:7 frac{1}{3}= frac{15}{2}: frac{22}{3}= frac{15}{2}* frac{3}{22}= frac{45}{44}$ $5 frac{1}{4}* frac{4}{21}= frac{21}{4}* frac{4}{21}=1$
$frac{15}{22}: frac{45}{44}= frac{15}{22}* frac{44}{45}= frac{2}{3}$