Bài 3:

a: \(\frac34\cdot\frac{16}{9}-\frac75:\frac{-21}{20}\)

\(=\frac{48}{36}+\frac75\cdot\frac{20}{21}=\frac43+\frac43=\frac83\)

b: \(2\frac13-\frac13\cdot\left\lbrack-\frac32+\left(\frac23+0,4\cdot5\right)\right\rbrack\)

\(=\frac73-\frac13\cdot\left\lbrack-\frac32+\frac23+2\right\rbrack\)

\(=\frac73-\frac13\cdot\frac{-9+4+12}{6}=\frac73-\frac13\cdot\frac76=\frac73\cdot\left(1-\frac16\right)=\frac73\cdot\frac56=\frac{35}{18}\)

c: \(\left(20+9\frac14\right):2\frac14\)

\(=\left(20+9,25\right):2,25\)

=29.25:2,25

=13

d: \(\left(6-2\frac45\right)\cdot3\frac18-1\frac35:\frac14\)

\(=\left(6-2-\frac45\right)\cdot\frac{25}{8}-\frac85\cdot4=\left(4-\frac45\right)\cdot\frac{25}{8}-\frac{32}{5}\)

\(=\frac{16}{5}\cdot\frac{25}{8}-\frac{32}{5}=10-\frac{32}{5}=\frac{18}{5}\)

e: \(\frac{32}{15}:\left(-1\frac15+1\frac13\right)\)

\(=\frac{32}{15}:\left(-1-\frac15+1+\frac13\right)=\frac{32}{15}:\frac{2}{15}=\frac{32}{2}=16\)

g: \(0,2\cdot\frac{15}{36}-\left(\frac25+\frac23\right):1\frac15\)

\(=\frac{3}{36}-\frac{6+10}{15}:\frac65=\frac{1}{12}-\frac{16}{15}\cdot\frac56=\frac{1}{12}-\frac89=\frac{3-32}{36}=-\frac{29}{36}\)

h: \(1\frac{13}{15}\cdot0,75-\left(\frac{8}{15}+0,25\right)\cdot\frac{24}{47}\)

\(=\frac{28}{15}\cdot\frac34-\left(\frac{8}{15}+\frac14\right)\cdot\frac{24}{47}=\frac75-\frac{32+15}{60}\cdot\frac{24}{47}\)

\(=\frac75-\frac25=1\)

g: \(5:\left(4\frac34-1\frac{25}{28}\right)-1\frac38:\left(\frac38+\frac{9}{20}\right)\)

\(=5:\left(\frac{19}{4}-\frac{53}{28}\right)-\frac{11}{8}:\left(\frac{15}{40}+\frac{18}{40}\right)\)

\(=5:\frac{80}{28}-\frac{11}{8}:\frac{33}{40}=5\cdot\frac{28}{80}-\frac{11}{8}\cdot\frac{40}{33}=5\cdot\frac{7}{20}-\frac53=\frac74-\frac53=\frac{21-20}{12}=\frac{1}{12}\)